MongoDB
What it is: Leading document-oriented NoSQL database. Store data as JSON-like documents. Flexible schema, horizontal scaling, rich query capabilities.
What It Does Best
Developer experience. Intuitive document model matches application objects. No ORM impedance mismatch. Fast iteration.
Flexible schema. Add fields without migrations. Polymorphic data models. Rapid prototyping to production.
Rich queries. Complex queries, aggregation framework, full-text search. More powerful than typical NoSQL databases.
Key Features
Document model: Store JSON/BSON documents with nested data
Aggregation framework: Powerful data processing pipelines
Sharding: Horizontal scaling across multiple servers
Replica sets: High availability with automatic failover
Atlas: Fully managed cloud database service
Pricing
Community Edition: Free, open source (self-hosted)
Atlas Free Tier: 512MB storage forever (shared cluster)
Atlas Serverless: $0.10 per million reads, $1.00 per million writes
Atlas Dedicated: From $57/month for smallest cluster
When to Use It
✅ Rapid application development with evolving schema
✅ Content management systems and catalogs
✅ User profiles and personalization
✅ Real-time analytics and caching
✅ Mobile and web applications
When NOT to Use It
❌ Complex multi-table joins (use relational database)
❌ Strong ACID transactions across documents (use PostgreSQL)
❌ Data warehouse analytics (use Snowflake, BigQuery)
❌ Highly normalized data models
❌ Need referential integrity enforcement
Common Use Cases
Content management: Articles, products, media with varied structures
User data: Profiles, preferences, activity logs
Product catalogs: E-commerce with flexible attributes
Mobile backends: Offline sync, flexible data models
Real-time applications: Gaming, chat, collaboration
MongoDB vs Alternatives
vs PostgreSQL: MongoDB better for flexible schemas, Postgres better for complex queries
vs DynamoDB: MongoDB more query flexibility, DynamoDB more scalable and managed
vs Cassandra: MongoDB better for queries, Cassandra better for massive write throughput
Unique Strengths
Document model: Natural fit for modern application development
Atlas: Best-in-class managed service with auto-scaling
Query richness: More powerful queries than most NoSQL databases
Ecosystem maturity: Drivers for every language, huge community
Bottom line: Most popular NoSQL database for good reason. Great developer experience, flexible schema, powerful queries. Best for applications with evolving data models. Don't use for complex analytics or when you need strict relational integrity. Atlas makes it easy to get started.