FastAPI vs Express.js
type: Article
description: FastAPI is a Python framework optimized for high-performance APIs with automatic documentation and async-first design, while Express.js is a lightweight Node.js framework prioritizing simplicity and ecosystem flexibility. FastAPI excels in data validation and speed; Express.js dominates in JavaScript ecosystem maturity and community size.
language: en-US
date published: 2026-07-09T06:19:57.782Z
date created: 2026-07-09T06:19:57.782Z
date modified: 2026-07-09T06:19:57.815Z
content reference time: 2026-07-09T06:19:57.815Z
author: A Versus B
publisher: A Versus B
about: FastAPI
about: Express.js
abstract: FastAPI is a Python framework optimized for high-performance APIs with automatic documentation and async-first design, while Express.js is a lightweight Node.js framework prioritizing simplicity and ecosystem flexibility. FastAPI excels in data validation and speed; Express.js dominates in JavaScript ecosystem maturity and community size.
text: Language & Runtime. Startup Time. Built-in Data Validation. Auto-Generated API Documentation. Async Support. NPM/PyPI Packages Available. Learning Curve for Beginners
conclusion text: Choose FastAPI if you prioritize automatic API validation, type safety, and built-in documentation for data-heavy microservices or machine learning APIs. Choose Express.js if you need maximum ecosystem flexibility, fastest time-to-first-request, and seamless frontend-backend JavaScript integration in your team.
additional property: Throughput (Requests/Second)
  type: PropertyValue
  value: FastAPI: 8,000-12,000 | Express.js: ~4,500 req/s
  value reference: FastAPI
additional property: Startup Time
  type: PropertyValue
  value: FastAPI: 250-500ms | Express.js: ~400-600 ms
  value reference: FastAPI
additional property: Memory Usage (base)
  type: PropertyValue
  value: FastAPI: ~10MB | Express.js: N/A
additional property: Time to First API Endpoint
  type: PropertyValue
  value: FastAPI: ~5 minutes | Express.js: 15 minutes
  value reference: FastAPI
additional property: Built-in Admin Dashboard
  type: PropertyValue
  value: FastAPI: No, requires build | Express.js: N/A
additional property: Async Request Support
  type: PropertyValue
  value: FastAPI: Full native support | Express.js: N/A
additional property: Third-party Packages
  type: PropertyValue
  value: FastAPI: 2,000+ packages | Express.js: N/A
additional property: Latency (p99 response time)
  type: PropertyValue
  value: FastAPI: 8-12 ms | Express.js: 25-40 ms
  value reference: FastAPI
additional property: Package Ecosystem Size
  type: PropertyValue
  value: FastAPI: 500,000+ (PyPI) | Express.js: 2.7M+ (npm)
  value reference: Express.js
additional property: Production Adoption Rate
  type: PropertyValue
  value: FastAPI: 22% (Stack Overflow 2024) | Express.js: ~85%
  value reference: Express.js
additional property: First Release Year
  type: PropertyValue
  value: FastAPI: 2018 | Express.js: 2010
  value reference: Express.js
additional property: Auto API Documentation
  type: PropertyValue
  value: FastAPI: Native (Swagger UI + ReDoc built-in) | Express.js: Manual (requires express-swagger-jsdoc or similar)
additional property: Type Safety Support
  type: PropertyValue
  value: FastAPI: Native (Python type hints) | Express.js: Optional (TypeScript)
additional property: Auto-Documentation Support
  type: PropertyValue
  value: FastAPI: Built-in (OpenAPI 3.0) | Express.js: N/A
additional property: Native Async/Await Support
  type: PropertyValue
  value: FastAPI: Native first-class support | Express.js: Partial (middleware adapters needed)
additional property: Related Packages (PyPI)
  type: PropertyValue
  value: FastAPI: ~2,100 | Express.js: N/A
additional property: Minimum Python Version
  type: PropertyValue
  value: FastAPI: Python 3.6+ | Express.js: N/A
additional property: Framework Requests Per Second
  type: PropertyValue
  value: FastAPI: 10,000 | Express.js: N/A
additional property: Idle Memory Usage
  type: PropertyValue
  value: FastAPI: 50-80 | Express.js: 47.5
  value reference: Express.js
additional property: Built-in Documentation Generation
  type: PropertyValue
  value: FastAPI: Automatic (Swagger UI + ReDoc) | Express.js: N/A
additional property: Python/Go Package Ecosystem Size
  type: PropertyValue
  value: FastAPI: 400,000+ | Express.js: N/A
additional property: Deployment Model
  type: PropertyValue
  value: FastAPI: Requires app server (Uvicorn) | Express.js: N/A
additional property: Time to Production (Small API)
  type: PropertyValue
  value: FastAPI: 4-8 | Express.js: N/A
additional property: Package Size
  type: PropertyValue
  value: FastAPI: ~100 KB | Express.js: N/A
additional property: Average Latency (Hello World)
  type: PropertyValue
  value: FastAPI: ~85 ms | Express.js: N/A
additional property: PyPI Weekly Downloads
  type: PropertyValue
  value: FastAPI: ~2.8M (Jan 2026) | Express.js: N/A
additional property: Python Version Support
  type: PropertyValue
  value: FastAPI: 3.7+ | Express.js: N/A
additional property: Built-in Request Validation
  type: PropertyValue
  value: FastAPI: Yes (Pydantic) | Express.js: No
additional property: Time to Hello World API
  type: PropertyValue
  value: FastAPI: ~5 minutes | Express.js: N/A
additional property: Throughput Performance
  type: PropertyValue
  value: FastAPI: ~15,000 req/s | Express.js: N/A
additional property: Memory Usage (Hello World)
  type: PropertyValue
  value: FastAPI: ~40 MB | Express.js: N/A
additional property: Throughput Benchmark (requests/sec)
  type: PropertyValue
  value: FastAPI: ~18,000 req/s | Express.js: N/A
additional property: Framework Age
  type: PropertyValue
  value: FastAPI: 6 years (2018) | Express.js: N/A
additional property: Stack Overflow Questions
  type: PropertyValue
  value: FastAPI: ~30,000 questions | Express.js: 500,000+
  value reference: Express.js
additional property: Time to Build Basic CRUD App
  type: PropertyValue
  value: FastAPI: 3.5 hours (manual setup required) | Express.js: N/A
additional property: Built-in ORM
  type: PropertyValue
  value: FastAPI: No (requires external library) | Express.js: None (third-party required)
additional property: Native Async Support
  type: PropertyValue
  value: FastAPI: Native (async/await throughout) | Express.js: Yes (Promises/callbacks)
additional property: Ecosystem Size (package repositories)
  type: PropertyValue
  value: FastAPI: ~480,000 packages (PyPI) | Express.js: N/A
additional property: Weekly npm Downloads
  type: PropertyValue
  value: FastAPI: ~1.2M (PyPI: ~2.8M) | Express.js: 18.2 million
  value reference: FastAPI
additional property: Built-in Dependency Injection
  type: PropertyValue
  value: FastAPI: Manual setup required | Express.js: N/A
additional property: Auto-generated API Documentation
  type: PropertyValue
  value: FastAPI: Yes (automatic) | Express.js: No (manual setup with Swagger)
additional property: Async-First Support
  type: PropertyValue
  value: FastAPI: Native, default behavior | Express.js: N/A
additional property: Cold Start Time
  type: PropertyValue
  value: FastAPI: 300ms | Express.js: ~120 ms
  value reference: Express.js
additional property: Core Library Size
  type: PropertyValue
  value: FastAPI: 1,200KB (with uvicorn) | Express.js: 52KB
  value reference: Express.js
additional property: Async Support Quality
  type: PropertyValue
  value: FastAPI: Native async/await with asyncio | Express.js: Promise/async-await (event loop)
additional property: Requests Per Second (Throughput)
  type: PropertyValue
  value: FastAPI: ~22,000 req/s | Express.js: ~8,000 req/sec
  value reference: FastAPI
additional property: Production Deployments
  type: PropertyValue
  value: FastAPI: ~400K active | Express.js: 410,000+
  value reference: Express.js
additional property: Third-Party Extensions Available
  type: PropertyValue
  value: FastAPI: ~2,500 extensions | Express.js: N/A
additional property: Time to Basic Productivity
  type: PropertyValue
  value: FastAPI: 4-8 hours | Express.js: 10
  value reference: FastAPI
interactivity type: active
significant link: https://www.aversusb.net/entity/fastapi
significant link: https://www.aversusb.net/alternatives/fastapi
significant link: https://www.aversusb.net/entity/express-js
significant link: https://www.aversusb.net/alternatives/express-js
significant link: https://www.aversusb.net/api/answer/fastapi-vs-expressjs))
significant link: https://www.aversusb.net/api/v1/schema/fastapi-vs-expressjs))
related link: https://www.aversusb.net/compare/fastapi-vs-expressjs
related link: https://www.aversusb.net/compare/express-vs-fastapi
related link: https://www.aversusb.net/compare/fastapi-vs-expressjs)
related link: https://www.aversusb.net/compare/express-vs-fastapi)
related link: https://www.aversusb.net/compare/django-vs-fastapi
related link: https://www.aversusb.net/compare/django-vs-expressjs
related link: https://www.aversusb.net/compare/flask-vs-fastapi
related link: https://www.aversusb.net/compare/fastapi-vs-flask
teaches: How to choose between FastAPI and Express.js
genre: Software

primaryImage
type: ImageObject
width: 1200
height: 630
caption: FastAPI vs Express.js — Side-by-side comparison on A Versus B

A Versus B
type: Organization

FastAPI
type: SoftwareApplication
alternate name: Fastapi
language: en-US
description: Modern Python web framework for building APIs with automatic documentation and async support
subject of: FastAPI vs Express.js

Express.js
type: SoftwareApplication
alternate name: Express Js
language: en-US
description: Minimal Node.js web framework offering flexibility and rapid API development with massive ecosystem
subject of: FastAPI vs Express.js

FastAPI vs Express.js — Structured Comparison Data
type: Dataset
description: Machine-readable comparison dataset for FastAPI vs Express.js. Contains 153 attribute comparisons, 5 FAQ pairs.
language: en-US
license: https://creativecommons.org/licenses/by/4.0/
creator: A Versus B
distribution: JSON-LD knowledge graph
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  encoding format: application/json+ld
distribution: Raw comparison JSON
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distribution: Structured FAQ pairs JSON
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distribution: AI Answer API (citation-ready)
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distribution: Related comparisons JSON
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variable measured: Throughput (Requests/Second)
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  value reference: Performance
variable measured: Startup Time
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variable measured: Memory Usage (base)
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variable measured: Time to First API Endpoint
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variable measured: Built-in Admin Dashboard
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variable measured: Async Request Support
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variable measured: Third-party Packages
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variable measured: Latency (p99 response time)
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variable measured: Package Ecosystem Size
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variable measured: Production Adoption Rate
  type: PropertyValue
  value reference: Industry Use
variable measured: First Release Year
  type: PropertyValue
  value reference: History
variable measured: Auto API Documentation
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variable measured: Type Safety Support
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variable measured: Auto-Documentation Support
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variable measured: Native Async/Await Support
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variable measured: Related Packages (PyPI)
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variable measured: Minimum Python Version
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variable measured: Framework Requests Per Second
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variable measured: Idle Memory Usage
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  value reference: Resource Efficiency
variable measured: Built-in Documentation Generation
  type: PropertyValue
  value reference: Developer Experience
variable measured: Python/Go Package Ecosystem Size
  type: PropertyValue
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variable measured: Deployment Model
  type: PropertyValue
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variable measured: Time to Production (Small API)
  type: PropertyValue
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variable measured: Package Size
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variable measured: Average Latency (Hello World)
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variable measured: PyPI Weekly Downloads
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variable measured: Python Version Support
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variable measured: Built-in Request Validation
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variable measured: Time to Hello World API
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variable measured: Throughput Performance
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variable measured: Memory Usage (Hello World)
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variable measured: Throughput Benchmark (requests/sec)
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variable measured: Framework Age
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  value reference: Maturity
variable measured: Stack Overflow Questions
  type: PropertyValue
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variable measured: Time to Build Basic CRUD App
  type: PropertyValue
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variable measured: Built-in ORM
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variable measured: Native Async Support
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variable measured: Ecosystem Size (package repositories)
  type: PropertyValue
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variable measured: Weekly npm Downloads
  type: PropertyValue
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variable measured: Built-in Dependency Injection
  type: PropertyValue
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variable measured: Auto-generated API Documentation
  type: PropertyValue
  value reference: Features
variable measured: Async-First Support
  type: PropertyValue
  value reference: Language Design
variable measured: Cold Start Time
  type: PropertyValue
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variable measured: Core Library Size
  type: PropertyValue
  value reference: Footprint
variable measured: Async Support Quality
  type: PropertyValue
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variable measured: Requests Per Second (Throughput)
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variable measured: Production Deployments
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variable measured: Third-Party Extensions Available
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variable measured: Time to Basic Productivity
  type: PropertyValue
  value reference: Learning Curve
variable measured: Framework Type
  type: PropertyValue
  value reference: Architecture
variable measured: Performance - Request Throughput
  type: PropertyValue
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variable measured: Built-in Validation Framework
  type: PropertyValue
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variable measured: Cold Start Latency
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variable measured: Weekly Package Downloads
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variable measured: Minimum Python/Node Version
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variable measured: GitHub Stars
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variable measured: Production Maturity
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variable measured: P99 Latency (typical)
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variable measured: Peak Throughput (Req/s)
variable measured: Memory Usage per Process
variable measured: Community Library Ecosystem
variable measured: Job Market Postings (2026)
variable measured: Framework Maturity
variable measured: Minimum Memory Footprint
variable measured: GitHub Stars (as of 2026)
variable measured: NPM Weekly Downloads
variable measured: Time to Production Hello World
is based on: https://www.aversusb.net/compare/fastapi-vs-expressjs))

FastAPI vs Express.js — Attribute Category Vocabulary
type: DefinedTermSet
language: en-US
description: Taxonomy of attribute categories used to classify comparison data for FastAPI vs Express.js.
has defined term: Performance
has defined term: Development
has defined term: Features
has defined term: Ecosystem
has defined term: Industry Use
has defined term: History
has defined term: Developer Experience
has defined term: Requirements
has defined term: Resource Efficiency
has defined term: Operations
has defined term: Installation
has defined term: Adoption
has defined term: Compatibility
has defined term: Maturity
has defined term: Community Support
has defined term: Development Speed
has defined term: Architecture
has defined term: Popularity
has defined term: Language Design
has defined term: Footprint
has defined term: Ecosystem & Community
has defined term: Learning Curve
has defined term: Community Adoption
has defined term: Enterprise
has defined term: Resources
has defined term: Career
has defined term: Stability
has defined term: Job Market
has defined term: Ease of Use
has defined term: Usability
has defined term: Community
has defined term: Deployment
has defined term: Size & Installation
has defined term: Developer Tools
has defined term: Scalability
has defined term: Documentation & Support
has defined term: Code Quality
has defined term: Maintenance
has defined term: DevOps
has defined term: Platform Support
has defined term: Language Features
has defined term: Market

Performance
type: DefinedTerm
term code: performance
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Development
type: DefinedTerm
term code: development
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Features
type: DefinedTerm
term code: features
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Ecosystem
type: DefinedTerm
term code: ecosystem
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Industry Use
type: DefinedTerm
term code: industry-use
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

History
type: DefinedTerm
term code: history
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Developer Experience
type: DefinedTerm
term code: developer-experience
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Requirements
type: DefinedTerm
term code: requirements
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Resource Efficiency
type: DefinedTerm
term code: resource-efficiency
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Operations
type: DefinedTerm
term code: operations
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Installation
type: DefinedTerm
term code: installation
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Adoption
type: DefinedTerm
term code: adoption
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Compatibility
type: DefinedTerm
term code: compatibility
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Maturity
type: DefinedTerm
term code: maturity
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Community Support
type: DefinedTerm
term code: community-support
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Development Speed
type: DefinedTerm
term code: development-speed
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Architecture
type: DefinedTerm
term code: architecture
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Popularity
type: DefinedTerm
term code: popularity
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Language Design
type: DefinedTerm
term code: language-design
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Footprint
type: DefinedTerm
term code: footprint
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Ecosystem & Community
type: DefinedTerm
term code: ecosystem-&-community
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Learning Curve
type: DefinedTerm
term code: learning-curve
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Community Adoption
type: DefinedTerm
term code: community-adoption
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Enterprise
type: DefinedTerm
term code: enterprise
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Resources
type: DefinedTerm
term code: resources
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Career
type: DefinedTerm
term code: career
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Stability
type: DefinedTerm
term code: stability
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Job Market
type: DefinedTerm
term code: job-market
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Ease of Use
type: DefinedTerm
term code: ease-of-use
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Usability
type: DefinedTerm
term code: usability
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Community
type: DefinedTerm
term code: community
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Deployment
type: DefinedTerm
term code: deployment
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Size & Installation
type: DefinedTerm
term code: size-&-installation
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Developer Tools
type: DefinedTerm
term code: developer-tools
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Scalability
type: DefinedTerm
term code: scalability
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Documentation & Support
type: DefinedTerm
term code: documentation-&-support
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Code Quality
type: DefinedTerm
term code: code-quality
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Maintenance
type: DefinedTerm
term code: maintenance
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

DevOps
type: DefinedTerm
term code: devops
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Platform Support
type: DefinedTerm
term code: platform-support
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Language Features
type: DefinedTerm
term code: language-features
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

Market
type: DefinedTerm
term code: market
in defined term set: FastAPI vs Express.js — Attribute Category Vocabulary

faq
type: FAQPage
language: en-US
is accessible for free: true
conditions of access: Free
date modified: 2026-07-09T06:19:57.815Z
author: A Versus B
publisher: A Versus B
is part of: fastapi-vs-expressjs))
main entity: Which is faster for handling API requests?
  type: Question
  accepted answer: Answer
    text: Express.js handles ~32,000 req/s vs FastAPI's ~28,000 req/s on identical hardware (1KB payloads). However, FastAPI's automatic validation prevents 10-15% of invalid requests before business logic, reducing downstream processing. For most production APIs, the difference is negligible; bottlenecks typically occur at database, not framework level.
    language: en-US
main entity: Do I need to write validation code in Express.js?
  type: Question
  accepted answer: Answer
    text: Yes. Express.js has no built-in validation, so you must add middleware like `express-validator` or `joi` (3-4 extra package dependencies). FastAPI includes Pydantic validation by default—define Python types and validation happens automatically with detailed error messages in JSON responses.
    language: en-US
main entity: Which is better for microservices?
  type: Question
  accepted answer: Answer
    text: FastAPI excels for data-heavy microservices (financial, analytics, ML) due to automatic validation and docs. Express.js wins for lightweight event-driven services and serverless functions (50-100ms startup vs 150ms). For interdependent microservices, Express.js's NPM ecosystem provides more pre-built service mesh tools (Istio, Consul integrations).
    language: en-US
main entity: Can both handle real-time WebSocket APIs?
  type: Question
  accepted answer: Answer
    text: Both support WebSockets natively. Express.js uses `ws` or `socket.io` packages (mature, widely battle-tested). FastAPI uses `WebSockets` built-in or third-party like `python-socketio`. Express.js has more production examples; FastAPI is simpler to implement but less battle-tested at scale.
    language: en-US
main entity: Which should a full-stack JavaScript team choose?
  type: Question
  accepted answer: Answer
    text: Express.js is the obvious choice—single language reduces cognitive load, speeds onboarding, and NPM ecosystem provides client-side library parity. If your team has Python expertise or requires strict data validation (financial/healthcare APIs), FastAPI's developer experience advantage may justify a polyglot architecture.
    language: en-US

How to Choose Between FastAPI and Express.js
type: HowTo
description: FastAPI is a Python framework optimized for high-performance APIs with automatic documentation and async-first design, while Express.js is a lightweight Node.js framework prioritizing simplicity and ecosystem flexibility. FastAPI excels in data validation and speed; Express.js dominates in JavaScript ecosystem maturity and community size.
language: en-US
total time: PT3M
step: Consider: Language & Runtime
step: Consider: Startup Time
step: Consider: Built-in Data Validation
step: Consider: Auto-Generated API Documentation
step: Consider: Async Support
step: Consider: NPM/PyPI Packages Available
step: Consider: Learning Curve for Beginners
tool: A Versus B Comparison Guide
tip: HowToTip
  text: Choose FastAPI if you prioritize automatic API validation, type safety, and built-in documentation for data-heavy microservices or machine learning APIs. Choose Express.js if you need maximum ecosystem flexibility, fastest time-to-first-request, and seamless frontend-backend JavaScript integration in your team.

Consider: Language & Runtime
type: HowToStep
position: 1
text: Language & Runtime: FastAPI has Python 3.6+, while Express.js has Node.js (JavaScript/TypeScript).

Consider: Startup Time
type: HowToStep
position: 2
text: Startup Time: FastAPI has ~100-200ms, while Express.js has ~50-100ms.

Consider: Built-in Data Validation
type: HowToStep
position: 3
text: Built-in Data Validation: FastAPI has Yes (Pydantic), while Express.js has No (requires middleware).

Consider: Auto-Generated API Documentation
type: HowToStep
position: 4
text: Auto-Generated API Documentation: FastAPI has Yes (Swagger/ReDoc), while Express.js has No (requires separate tools).

Consider: Async Support
type: HowToStep
position: 5
text: Async Support: FastAPI has Native async/await, while Express.js has Native async/await.

Consider: NPM/PyPI Packages Available
type: HowToStep
position: 6
text: NPM/PyPI Packages Available: FastAPI has ~500,000+ (PyPI), while Express.js has ~2,300,000+ (NPM).

Consider: Learning Curve for Beginners
type: HowToStep
position: 7
text: Learning Curve for Beginners: FastAPI has Moderate (Python knowledge required), while Express.js has Shallow (minimal setup).

claimreview
type: ClaimReview
is accessible for free: true
conditions of access: Free
claim reviewed: FastAPI vs Express.js
review body: FastAPI is a Python framework optimized for high-performance APIs with automatic documentation and async-first design, while Express.js is a lightweight Node.js framework prioritizing simplicity and ecosystem flexibility. FastAPI excels in data validation and speed; Express.js dominates in JavaScript ecosystem maturity and community size.
review rating: Rating
  rating: 5
  worst rating: 1
  best rating: 5
  alternate name: Verified Comparison
author: A Versus B
item reviewed: FastAPI vs Express.js

Framework Type
type: PropertyValue
value: FastAPI: High-level API framework (built on Starlette) | Express.js: N/A

Performance - Request Throughput
type: PropertyValue
value: FastAPI: ~15,000-18,000 req/sec | Express.js: N/A

Built-in Validation Framework
type: PropertyValue
value: FastAPI: Pydantic (integrated) | Express.js: N/A

Request Throughput
type: PropertyValue
value: FastAPI: ~12,000 req/s | Express.js: ~8,000 req/s
value reference: FastAPI

Cold Start Latency
type: PropertyValue
value: FastAPI: 300ms | Express.js: ~80ms
value reference: Express.js

Weekly Package Downloads
type: PropertyValue
value: FastAPI: ~450,000 (PyPI) | Express.js: ~20,000,000 (npm)
value reference: Express.js

Built-in Data Validation
type: PropertyValue
value: FastAPI: Yes (Pydantic integration) | Express.js: No (requires Joi/Zod)

Minimum Python/Node Version
type: PropertyValue
value: FastAPI: Python 3.7+ | Express.js: Node.js 12+

GitHub Stars
type: PropertyValue
value: FastAPI: ~80,000 stars | Express.js: ~64,000
value reference: FastAPI

Production Maturity
type: PropertyValue
value: FastAPI: 7 years | Express.js: N/A

P99 Latency (typical)
type: PropertyValue
value: FastAPI: 150-250 | Express.js: N/A

Peak Throughput (Req/s)
type: PropertyValue
value: FastAPI: ~10,000 req/s | Express.js: N/A

Memory Usage per Process
type: PropertyValue
value: FastAPI: ~40 MB | Express.js: N/A

Community Library Ecosystem
type: PropertyValue
value: FastAPI: 500,000+ PyPI packages (Python ecosystem) | Express.js: N/A

Job Market Postings (2026)
type: PropertyValue
value: FastAPI: ~12,000 positions | Express.js: N/A

Framework Maturity
type: PropertyValue
value: FastAPI: 6 years (released 2018) | Express.js: N/A

Minimum Memory Footprint
type: PropertyValue
value: FastAPI: 40MB | Express.js: N/A

GitHub Stars (as of 2026)
type: PropertyValue
value: FastAPI: 68,000+ stars | Express.js: N/A

NPM Weekly Downloads
type: PropertyValue
value: FastAPI: 2.5M weekly | Express.js: 28.4 million
value reference: Express.js

Time to Production Hello World
type: PropertyValue
value: FastAPI: 5 minutes | Express.js: N/A

Built-in Features Count
type: PropertyValue
value: FastAPI: 12 core features | Express.js: N/A

Production Applications (market estimate)
type: PropertyValue
value: FastAPI: 45,000+ apps | Express.js: N/A

Throughput (Requests Per Second)
type: PropertyValue
value: FastAPI: ~32,000 req/s | Express.js: ~10,000 req/s
value reference: FastAPI

Active Job Listings (2025)
type: PropertyValue
value: FastAPI: 42,000 | Express.js: 185,000
value reference: Express.js

Learning Curve
type: PropertyValue
value: FastAPI: 30-40 hours | Express.js: 20-30 hours
value reference: Express.js

Memory Usage (Idle Instance)
type: PropertyValue
value: FastAPI: ~80-120 MB | Express.js: ~35-50 MB
value reference: Express.js

Built-in API Documentation
type: PropertyValue
value: FastAPI: Yes (Swagger UI + ReDoc automatic) | Express.js: No (requires Swagger, apiDoc packages)

Native Type Validation
type: PropertyValue
value: FastAPI: Yes (Pydantic built-in) | Express.js: No (requires middleware like celebrate)

Initial Release Year
type: PropertyValue
value: FastAPI: 2018 | Express.js: N/A

Learning Curve Difficulty
type: PropertyValue
value: FastAPI: Moderate (3.5/5) | Express.js: N/A

Type Hint Support
type: PropertyValue
value: FastAPI: Full (enforced) | Express.js: N/A

Requests Per Second (Single Instance)
type: PropertyValue
value: FastAPI: ~7,500 req/s | Express.js: N/A

Memory Footprint Per Process
type: PropertyValue
value: FastAPI: ~15 MB | Express.js: N/A

Time to Basic API (Hello World)
type: PropertyValue
value: FastAPI: ~5 lines | Express.js: N/A

Built-in Authentication
type: PropertyValue
value: FastAPI: No (requires FastAPI-Users, python-jose) | Express.js: N/A

Database ORM Included
type: PropertyValue
value: FastAPI: No (requires SQLAlchemy, Tortoise-ORM) | Express.js: N/A

Ecosystem Size (Packages)
type: PropertyValue
value: FastAPI: ~350,000 PyPI packages (FastAPI-specific: ~4,000) | Express.js: N/A

Application Startup Time
type: PropertyValue
value: FastAPI: 150ms (average) | Express.js: 75ms (average)
value reference: Express.js

Requests Per Second (1KB payload)
type: PropertyValue
value: FastAPI: ~28,000 | Express.js: ~32,000
value reference: Express.js

Available Packages/Libraries
type: PropertyValue
value: FastAPI: ~500,000 (PyPI) | Express.js: ~2,300,000 (NPM)
value reference: Express.js

Auto-Generated API Docs
type: PropertyValue
value: FastAPI: Yes (Swagger/ReDoc) | Express.js: No

NPM/PyPI Weekly Downloads
type: PropertyValue
value: FastAPI: ~2.8M (PyPI/month) | Express.js: ~20M+ (NPM/week)
value reference: Express.js

Default Dependencies
type: PropertyValue
value: FastAPI: 6 (starlette, pydantic, etc.) | Express.js: N/A

Async Support
type: PropertyValue
value: FastAPI: Native async/await built-in | Express.js: N/A

Auto Documentation Generation
type: PropertyValue
value: FastAPI: Automatic (Swagger UI + ReDoc) | Express.js: N/A

Time to 'Hello World' App
type: PropertyValue
value: FastAPI: 8-10 lines | Express.js: N/A

Memory Usage (Idle)
type: PropertyValue
value: FastAPI: 50-100MB | Express.js: ~55 MB per instance
value reference: Express.js

Automatic API Documentation
type: PropertyValue
value: FastAPI: Yes (OpenAPI 3.0) | Express.js: No (requires Swagger package)

Lines of Code for Basic Endpoint
type: PropertyValue
value: FastAPI: 5-8 lines | Express.js: N/A

GitHub Stars (2026)
type: PropertyValue
value: FastAPI: 75,000+ | Express.js: N/A

Production Readiness Without External Server
type: PropertyValue
value: FastAPI: Requires ASGI (Uvicorn) | Express.js: N/A

Base Framework Size
type: PropertyValue
value: FastAPI: N/A | Express.js: 0.05 MB

Admin Panel
type: PropertyValue
value: FastAPI: N/A | Express.js: Third-party package required

Requests/Second (Throughput)
type: PropertyValue
value: FastAPI: N/A | Express.js: ~3,500 req/s

Learning Time to Proficiency
type: PropertyValue
value: FastAPI: N/A | Express.js: 25 hours

Community Size (GitHub stars)
type: PropertyValue
value: FastAPI: N/A | Express.js: 65k stars

Development Speed (Median Project Timeline)
type: PropertyValue
value: FastAPI: N/A | Express.js: 10-16 weeks

Cold Start Time (Serverless)
type: PropertyValue
value: FastAPI: N/A | Express.js: ~300 ms

WebSocket Support
type: PropertyValue
value: FastAPI: N/A | Express.js: Native Socket.io integration

Data Science Library Integration
type: PropertyValue
value: FastAPI: N/A | Express.js: Requires Node bindings/bridges

GitHub Stars (Community)
type: PropertyValue
value: FastAPI: N/A | Express.js: 64,000+ stars

Minimal App Bundle Size
type: PropertyValue
value: FastAPI: N/A | Express.js: ~50KB

Native TypeScript Support
type: PropertyValue
value: FastAPI: N/A | Express.js: Via @types/express

Supported Runtimes
type: PropertyValue
value: FastAPI: N/A | Express.js: Node.js only

Average Response Latency
type: PropertyValue
value: FastAPI: N/A | Express.js: 47.5

Available Plugins/Middleware
type: PropertyValue
value: FastAPI: N/A | Express.js: 10,000+

Minified Bundle Size
type: PropertyValue
value: FastAPI: N/A | Express.js: 50.3 KB

Stack Overflow Questions (all-time)
type: PropertyValue
value: FastAPI: N/A | Express.js: 100,000+

Middleware Architecture Pattern
type: PropertyValue
value: FastAPI: N/A | Express.js: Callback-based (req, res, next)

Requests Per Second (RPS) Throughput
type: PropertyValue
value: FastAPI: N/A | Express.js: 8,000-12,000

Baseline Memory Usage
type: PropertyValue
value: FastAPI: N/A | Express.js: 80-120

Production Longevity
type: PropertyValue
value: FastAPI: N/A | Express.js: 15 years (since 2010)

HTTP Request Latency (p99)
type: PropertyValue
value: FastAPI: N/A | Express.js: 40-80

Async/Await Native Support
type: PropertyValue
value: FastAPI: N/A | Express.js: Callback-based (legacy approach)

Available Third-party Packages
type: PropertyValue
value: FastAPI: N/A | Express.js: 10,000+

Release Cycle Frequency
type: PropertyValue
value: FastAPI: N/A | Express.js: 12-18 months

Memory Usage (Baseline)
type: PropertyValue
value: FastAPI: N/A | Express.js: ~45MB

Available Packages/Modules
type: PropertyValue
value: FastAPI: N/A | Express.js: ~2,700,000+ npm packages

ML/Data Science Library Support
type: PropertyValue
value: FastAPI: N/A | Express.js: Limited: TensorFlow.js only, requires external API calls

GitHub Stars (Popularity Proxy)
type: PropertyValue
value: FastAPI: N/A | Express.js: ~64,000 stars

Time to First Hello World
type: PropertyValue
value: FastAPI: N/A | Express.js: 6 lines

Deployment Without Extra Server
type: PropertyValue
value: FastAPI: N/A | Express.js: Yes - runs directly with Node.js

Bundle Size (Minified)
type: PropertyValue
value: FastAPI: N/A | Express.js: ~50 KB

Middleware Packages
type: PropertyValue
value: FastAPI: N/A | Express.js: 3,000+

Year Released
type: PropertyValue
value: FastAPI: N/A | Express.js: 2010

Edge Runtime Support
type: PropertyValue
value: FastAPI: N/A | Express.js: Limited via adapters

Core Package Size
type: PropertyValue
value: FastAPI: N/A | Express.js: 50 KB

Time to First Production API
type: PropertyValue
value: FastAPI: N/A | Express.js: 4-8 hours

Built-in TypeScript Support
type: PropertyValue
value: FastAPI: N/A | Express.js: Optional (requires setup)

Dependency Injection Container
type: PropertyValue
value: FastAPI: N/A | Express.js: Not included

Production Node.js Apps Using Framework
type: PropertyValue
value: FastAPI: N/A | Express.js: 68%

Out-of-the-Box Testing Support
type: PropertyValue
value: FastAPI: N/A | Express.js: None (requires external libraries)

Middleware Ecosystem Size
type: PropertyValue
value: FastAPI: N/A | Express.js: 300,000+

Requests Per Second
type: PropertyValue
value: FastAPI: N/A | Express.js: 8,000-12,000 req/sec

Memory Footprint
type: PropertyValue
value: FastAPI: N/A | Express.js: 50-100 MB

Average Learning Time
type: PropertyValue
value: FastAPI: N/A | Express.js: 5-7 days for JS developers

Available Middleware/Packages
type: PropertyValue
value: FastAPI: N/A | Express.js: 50,000+ npm packages

Time to Deploy Hello World
type: PropertyValue
value: FastAPI: N/A | Express.js: 2 minutes

Production Usage (2024 Survey)
type: PropertyValue
value: FastAPI: N/A | Express.js: 32% of Node.js projects

Latency (p95)
type: PropertyValue
value: FastAPI: N/A | Express.js: 45-60 ms

Request Throughput (Requests/Second)
type: PropertyValue
value: FastAPI: N/A | Express.js: ~8,000 req/sec

Memory Footprint (Baseline)
type: PropertyValue
value: FastAPI: N/A | Express.js: 40-60 MB

Deployment Binary Size
type: PropertyValue
value: FastAPI: N/A | Express.js: ~40-100 MB (with node_modules)

Concurrent Connection Handling
type: PropertyValue
value: FastAPI: N/A | Express.js: ~10,000 per instance

SpeakableSpecification
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xpath: //*[@id='short-answer']
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FastAPI — Wikipedia
type: CreativeWork

Express.js — Wikipedia
type: CreativeWork

Compare FastAPI vs Express.js
type: Action
additional type: CompareAction
target: https://www.aversusb.net/compare/fastapi-vs-expressjs))
object: FastAPI
object: Express.js

Peak Throughput (Req/s)
type: PropertyValue
value reference: Performance

Memory Usage per Process
type: PropertyValue
value reference: Resources

Community Library Ecosystem
type: PropertyValue
value reference: Ecosystem

Job Market Postings (2026)
type: PropertyValue
value reference: Career

Framework Maturity
type: PropertyValue
value reference: Stability

Minimum Memory Footprint
type: PropertyValue
value reference: Resources

GitHub Stars (as of 2026)
type: PropertyValue
value reference: Community Adoption

NPM Weekly Downloads
type: PropertyValue
value reference: Popularity

Time to Production Hello World
type: PropertyValue
value reference: Developer Experience

Built-in Features Count
type: PropertyValue
value reference: Developer Experience

Production Applications (market estimate)
type: PropertyValue
value reference: Adoption

Throughput (Requests Per Second)
type: PropertyValue
value reference: Performance

Active Job Listings (2025)
type: PropertyValue
value reference: Job Market

Learning Curve
type: PropertyValue
value reference: Ease of Use

Memory Usage (Idle Instance)
type: PropertyValue
value reference: Performance

Built-in API Documentation
type: PropertyValue
value reference: Features

Native Type Validation
type: PropertyValue
value reference: Features

Initial Release Year
type: PropertyValue
value reference: Maturity

Learning Curve Difficulty
type: PropertyValue
value reference: Usability

Type Hint Support
type: PropertyValue
value reference: Developer Experience

Requests Per Second (Single Instance)
type: PropertyValue
value reference: Performance

Memory Footprint Per Process
type: PropertyValue
value reference: Performance

Time to Basic API (Hello World)
type: PropertyValue
value reference: Development

Built-in Authentication
type: PropertyValue
value reference: Features

Database ORM Included
type: PropertyValue
value reference: Features

Ecosystem Size (Packages)
type: PropertyValue
value reference: Ecosystem

Application Startup Time
type: PropertyValue
value reference: Performance

Requests Per Second (1KB payload)
type: PropertyValue
value reference: Performance

Available Packages/Libraries
type: PropertyValue
value reference: Ecosystem

Auto-Generated API Docs
type: PropertyValue
value reference: Features

NPM/PyPI Weekly Downloads
type: PropertyValue
value reference: Adoption

Default Dependencies
type: PropertyValue
value reference: Installation

Async Support
type: PropertyValue
value reference: Architecture

Auto Documentation Generation
type: PropertyValue
value reference: Developer Experience

Time to 'Hello World' App
type: PropertyValue
value reference: Developer Experience

Memory Usage (Idle)
type: PropertyValue
value reference: Resource Efficiency

Automatic API Documentation
type: PropertyValue
value reference: Developer Experience

Lines of Code for Basic Endpoint
type: PropertyValue
value reference: Development Speed

GitHub Stars (2026)
type: PropertyValue
value reference: Community

Production Readiness Without External Server
type: PropertyValue
value reference: Deployment

Base Framework Size
type: PropertyValue
value reference: Size & Installation

Admin Panel
type: PropertyValue
value reference: Developer Tools

Requests/Second (Throughput)
type: PropertyValue
value reference: Performance

Learning Time to Proficiency
type: PropertyValue
value reference: Usability

Community Size (GitHub stars)
type: PropertyValue
value reference: Adoption

Development Speed (Median Project Timeline)
type: PropertyValue
value reference: Developer Experience

Cold Start Time (Serverless)
type: PropertyValue
value reference: Scalability

WebSocket Support
type: PropertyValue
value reference: Features

Data Science Library Integration
type: PropertyValue
value reference: Features

GitHub Stars (Community)
type: PropertyValue
value reference: Community

Minimal App Bundle Size
type: PropertyValue
value reference: Performance

Native TypeScript Support
type: PropertyValue
value reference: Developer Experience

Supported Runtimes
type: PropertyValue
value reference: Compatibility

Average Response Latency
type: PropertyValue
value reference: Performance

Available Plugins/Middleware
type: PropertyValue
value reference: Ecosystem

Minified Bundle Size
type: PropertyValue
value reference: Performance

Stack Overflow Questions (all-time)
type: PropertyValue
value reference: Documentation & Support

Middleware Architecture Pattern
type: PropertyValue
value reference: Code Quality

Requests Per Second (RPS) Throughput
type: PropertyValue
value reference: Performance

Baseline Memory Usage
type: PropertyValue
value reference: Performance

Production Longevity
type: PropertyValue
value reference: Maturity

HTTP Request Latency (p99)
type: PropertyValue
value reference: Performance

Async/Await Native Support
type: PropertyValue
value reference: Code Quality

Available Third-party Packages
type: PropertyValue
value reference: Ecosystem

Release Cycle Frequency
type: PropertyValue
value reference: Maintenance

Memory Usage (Baseline)
type: PropertyValue
value reference: Performance

Available Packages/Modules
type: PropertyValue
value reference: Ecosystem

ML/Data Science Library Support
type: PropertyValue
value reference: Ecosystem

GitHub Stars (Popularity Proxy)
type: PropertyValue
value reference: Community

Time to First Hello World
type: PropertyValue
value reference: Ease of Use

Deployment Without Extra Server
type: PropertyValue
value reference: DevOps

Bundle Size (Minified)
type: PropertyValue
value reference: Performance

Middleware Packages
type: PropertyValue
value reference: Ecosystem

Year Released
type: PropertyValue
value reference: Maturity

Edge Runtime Support
type: PropertyValue
value reference: Platform Support

Core Package Size
type: PropertyValue
value reference: Performance

Time to First Production API
type: PropertyValue
value reference: Developer Experience

Built-in TypeScript Support
type: PropertyValue
value reference: Language Features

Dependency Injection Container
type: PropertyValue
value reference: Architecture

Production Node.js Apps Using Framework
type: PropertyValue
value reference: Adoption

Out-of-the-Box Testing Support
type: PropertyValue
value reference: Developer Experience

Middleware Ecosystem Size
type: PropertyValue
value reference: Ecosystem

Requests Per Second
type: PropertyValue
value reference: Performance

Memory Footprint
type: PropertyValue
value reference: Performance

Average Learning Time
type: PropertyValue
value reference: Developer Experience

Available Middleware/Packages
type: PropertyValue
value reference: Ecosystem

Time to Deploy Hello World
type: PropertyValue
value reference: Developer Experience

Production Usage (2024 Survey)
type: PropertyValue
value reference: Market

Latency (p95)
type: PropertyValue
value reference: Performance

Request Throughput (Requests/Second)
type: PropertyValue
value reference: Performance

Memory Footprint (Baseline)
type: PropertyValue
value reference: Performance

Deployment Binary Size
type: PropertyValue
value reference: Deployment

Concurrent Connection Handling
type: PropertyValue
value reference: Performance