PostgreSQL is a relational SQL database excelling at structured data with ACID compliance and complex queries, while MongoDB is a NoSQL document database optimized for flexible, unstructured data and horizontal scaling. The choice depends on your data structure and consistency requirements.
MongoDB vs PostgreSQL — Side-by-side comparison on A Versus B
NoSQL document database for flexible, scalable applications with JSON-like data structures.
Free, open-source relational database with advanced features and full control
Data Model. Transaction Support. Query Language. Horizontal Scaling. Schema Flexibility. Join Operations. Typical Deployment Cost
Choose PostgreSQL if you have structured, relational data with complex queries, need guaranteed ACID compliance across all operations, and want lower hosting costs. Choose MongoDB if you need schema flexibility, rapid prototyping, massive horizontal scalability, or work with semi-structured/nested JSON data like real-time analytics or content management systems.
MongoDB: Multi-document ACID (since v4.0, snapshot isolation) | PostgreSQL: N/A
MongoDB: Native automatic sharding across nodes | PostgreSQL: Manual sharding required
MongoDB: 8-12ms for equivalent queries | PostgreSQL: N/A
MongoDB: 24-36GB working set | PostgreSQL: N/A
MongoDB: 19 years (MongoDB 1.0 released 2009) | PostgreSQL: N/A
MongoDB: 100,000-500,000 ops/sec | PostgreSQL: N/A
MongoDB: 28% of web applications (Stack Overflow 2024) | PostgreSQL: N/A
MongoDB: ACID from v4.0 (slower than PostgreSQL) | PostgreSQL: Full multi-statement ACID
Query Language Complexity (learning curve)
MongoDB: 2-4 weeks (MongoDB Query Language simpler syntax) | PostgreSQL: 1-2 months (SQL standardized, widely taught)
MongoDB: MongoDB Atlas managed cloud (SaaS); community edition free | PostgreSQL: Free open-source; commercial support available
MongoDB: 250-350 MB | PostgreSQL: 150-200 MB
MongoDB: 10+ (single field, compound, geospatial, text, wildcard) | PostgreSQL: 20+ (B-tree, hash, BRIN, GiST, partial indexes)
MongoDB: 0 GB (Atlas free tier discontinued) | PostgreSQL: N/A
MongoDB: Multi-document (v4.0+) | PostgreSQL: N/A
MongoDB: Unlimited (sharding dependent) | PostgreSQL: N/A
MongoDB: MongoDB Query Language (MQL) | PostgreSQL: N/A
MongoDB: Manual sharding + Atlas auto-scaling | PostgreSQL: N/A
MongoDB: Not enforced natively | PostgreSQL: N/A
MongoDB: 200+ query operators, joins, aggregation pipeline | PostgreSQL: N/A
MongoDB: 5-10ms (cluster dependent) | PostgreSQL: N/A
MongoDB: $57 (M10 Atlas cluster) | PostgreSQL: $20-50 (cloud VM minimum)
MongoDB: Multi-document ACID across collections | PostgreSQL: N/A
MongoDB: Manual sharding configuration required | PostgreSQL: N/A
MongoDB: 10,000-50,000 ops/sec | PostgreSQL: N/A
MongoDB: Moderate to high (backups, sharding, monitoring) | PostgreSQL: N/A
Query Complexity (Aggregation Capability)
MongoDB: 9 (full aggregation pipeline) | PostgreSQL: N/A
MongoDB: Unlimited (scales with cluster) | PostgreSQL: 1,000+
MongoDB: 5-10 days (custom code) | PostgreSQL: N/A
MongoDB: No (third-party only) | PostgreSQL: N/A
MongoDB: Change Streams (enterprise feature) | PostgreSQL: N/A
MongoDB: Schema-less (dynamic fields) | PostgreSQL: Fixed schema (requires ALTER)
MongoDB: Unlimited (sharding across clusters) | PostgreSQL: N/A
MongoDB: High (infrastructure management needed) | PostgreSQL: N/A
MongoDB: 38 ms (indexed query) | PostgreSQL: N/A
MongoDB: Manual API layer required | PostgreSQL: N/A
MongoDB: ~50,000 (sharded cluster) | PostgreSQL: ~10,000 (single node)
MongoDB: Multi-document (v4.0+, with limitations) | PostgreSQL: Full compliance, all operations
Storage Overhead (vs Equivalent Relational)
MongoDB: 2-3x larger (denormalization) | PostgreSQL: 1x baseline (normalized)
MongoDB: Yes (automatic sharding) | PostgreSQL: No (requires partitioning/third-party)
MongoDB: Aggregation pipeline (moderate for complex queries) | PostgreSQL: Full SQL with unlimited JOIN depth and CTEs
MongoDB: Optional/flexible (schema-on-read) | PostgreSQL: Required (schema-on-write)
MongoDB: ~25k stars | PostgreSQL: ~15k stars
MongoDB: 4-8 hours (managed cloud option available) | PostgreSQL: 2-4 hours (widely supported, simpler setup)
MongoDB: MQL (simpler for simple queries, steeper for complex joins) | PostgreSQL: SQL (steep initial curve, powerful at scale)
MongoDB: Multi-document transactions (4.0+) | PostgreSQL: Full transaction coverage (all operations)
MongoDB: Native, automatic shard distribution | PostgreSQL: Requires external tools (Citus, pg_partman)
MongoDB: $57 (Atlas M10) | PostgreSQL: $15 (RDS free tier + $20)
MongoDB: 25-40% (document format, field duplication) | PostgreSQL: 5-15% (optimized row format)
MongoDB: 8-15+ seconds ($lookup) | PostgreSQL: 0.5-2 seconds (optimized joins)
MongoDB: Limited (core features only) | PostgreSQL: 75+ community extensions
MongoDB: N/A | PostgreSQL: Complete (all operations)
MongoDB: N/A | PostgreSQL: ~25,000 (PostgreSQL 18)
MongoDB: N/A | PostgreSQL: ~320 (5-table join)
MongoDB: N/A | PostgreSQL: JSONB with full indexing
MongoDB: N/A | PostgreSQL: ~150 (minimal config)
MongoDB: N/A | PostgreSQL: Native pgvector
MongoDB: N/A | PostgreSQL: Comprehensive native support
MongoDB: N/A | PostgreSQL: TimescaleDB extension native
MongoDB: N/A | PostgreSQL: $15.25 (PostgreSQL 18)
MongoDB: N/A | PostgreSQL: 5 (14-18 active)
MongoDB: N/A | PostgreSQL: EDB, multiple vendors
MongoDB: N/A | PostgreSQL: 35,000 writes/sec
MongoDB: N/A | PostgreSQL: 1 (single instance)
MongoDB: N/A | PostgreSQL: Manual, typically 5-15 minutes
MongoDB: N/A | PostgreSQL: 100% (native)
MongoDB: N/A | PostgreSQL: $0 (open-source)
MongoDB: N/A | PostgreSQL: $0 (infrastructure cost only)
MongoDB: N/A | PostgreSQL: 30-60 minutes
MongoDB: N/A | PostgreSQL: 120-1440 minutes (self-hosted)
MongoDB: N/A | PostgreSQL: 0 (requires third-party)
MongoDB: N/A | PostgreSQL: Not native - requires extensions
MongoDB: N/A | PostgreSQL: Unlimited (petabyte+ capable)
MongoDB: N/A | PostgreSQL: Not included - manual setup required
MongoDB: N/A | PostgreSQL: Zero - 100% portable SQL
Supported Concurrent Connections (Free Tier)
MongoDB: N/A | PostgreSQL: Unlimited (depends on installation)
MongoDB: N/A | PostgreSQL: $0 (self-hosted only)
MongoDB: N/A | PostgreSQL: 240-1440 minutes (4-24 hours)
MongoDB: N/A | PostgreSQL: Unlimited (self-hosted)
MongoDB: N/A | PostgreSQL: Unlimited (hardware dependent)
MongoDB: N/A | PostgreSQL: Manual or third-party tools required
MongoDB: N/A | PostgreSQL: Customizable via WAL archiving
MongoDB: N/A | PostgreSQL: $50-200+ (self-hosted infrastructure) or $100-500 (managed provider)
MongoDB: N/A | PostgreSQL: Manual; requires 5-60 minutes intervention
MongoDB: N/A | PostgreSQL: Unlimited (hardware-dependent)
MongoDB: N/A | PostgreSQL: Trivial (native format, zero lock-in)
MongoDB: N/A | PostgreSQL: 500+ (all available from PostgreSQL ecosystem)
MongoDB: N/A | PostgreSQL: 0 seconds (always running)
MongoDB: N/A | PostgreSQL: 10,000,000+ deployments globally
Complex Analytical Query Speed (with JOINs + aggregations)
MongoDB: N/A | PostgreSQL: 320ms (with window functions)
MongoDB: N/A | PostgreSQL: Yes (default)
MongoDB: N/A | PostgreSQL: 15+ languages
MongoDB: N/A | PostgreSQL: 85% of providers
MongoDB: N/A | PostgreSQL: Yes (since 8.4)
MongoDB: N/A | PostgreSQL: 52ms (PostgreSQL)
Complex Analytical Query Speed (Aggregate + Join)
MongoDB: N/A | PostgreSQL: 850ms (PostgreSQL)
MongoDB: N/A | PostgreSQL: Yes, comprehensive with operators and indexing
MongoDB: N/A | PostgreSQL: Native with ranking, stemming, 15+ languages
MongoDB: N/A | PostgreSQL: Full support with 20+ window functions
MongoDB: N/A | PostgreSQL: Unlimited (manual setup)
MongoDB: N/A | PostgreSQL: None standard
MongoDB: N/A | PostgreSQL: Limited by hardware
MongoDB: N/A | PostgreSQL: Latest (16.2)
MongoDB: N/A | PostgreSQL: Depends on setup (50-500ms typical)
How to choose between MongoDB and PostgreSQL
MongoDB vs PostgreSQL — Structured Comparison Data
Machine-readable comparison dataset for MongoDB vs PostgreSQL. Contains 131 attribute comparisons, 5 FAQ pairs.
MongoDB vs PostgreSQL — Attribute Category Vocabulary
Taxonomy of attribute categories used to classify comparison data for MongoDB vs PostgreSQL.
It depends on the use case. MongoDB excels at write-heavy, unstructured workloads and can be 30-50% faster for simple document retrieval. PostgreSQL is 5-15x faster for complex queries with multiple joins. For your specific scenario, benchmark both with your actual query patterns.
PostgreSQL is better for most startups due to 3x lower hosting costs ($15-20/month vs $57+), extensive documentation, and SQL familiarity. MongoDB is ideal only if you need rapid schema changes or are building high-scale distributed systems from day one.
Not for all applications. MongoDB works well for content management, real-time analytics, and nested data. PostgreSQL is essential for financial systems, e-commerce, and applications requiring strong consistency. Many enterprises use both (polyglot persistence).
PostgreSQL managed services (AWS RDS, DigitalOcean) start at $15-20/month. MongoDB Atlas starts at $57/month for M10. For equivalent performance, MongoDB costs 2-3x more. Self-hosted PostgreSQL is free but requires DevOps expertise.
Which has better community support in 2026?
PostgreSQL has 30+ years of maturity with 200K+ Stack Overflow questions and enterprise backing. MongoDB has 4.2M+ npm downloads monthly with strong commercial support from MongoDB Inc. Both have excellent communities; PostgreSQL edges ahead for legacy system support.
How to Choose Between MongoDB and PostgreSQL
Data Model: MongoDB has Document-based (JSON/BSON), while PostgreSQL has Relational (Tables/Rows).
Transaction Support: MongoDB has Multi-document ACID (v4.0+), while PostgreSQL has Full ACID across all operations.
Query Language: MongoDB has MongoDB Query Language (MQL), while PostgreSQL has SQL.
Horizontal Scaling: MongoDB has Native sharding built-in, while PostgreSQL has Requires third-party solutions.
Schema Flexibility: MongoDB has Schema-less (dynamic), while PostgreSQL has Fixed schema required.
Join Operations: MongoDB has $lookup (limited performance), while PostgreSQL has Native joins (optimized).
Typical Deployment Cost: MongoDB has $57-300/month (Atlas M10-M30), while PostgreSQL has $15-100/month (RDS/Managed).