Indexing and query strategies compared#
Query capabilities are often the deciding factor when choosing between MongoDB and DynamoDB. Both databases now offer more advanced options than before, but they approach indexing differently:
MongoDB supports rich secondary indexes, compound indexes, and full-text search. You can query on any field without major schema changes, which is ideal for dynamic applications.
DynamoDB uses Global Secondary Indexes (GSI) and Local Secondary Indexes (LSI) to extend query capabilities. While these require more upfront design, they can deliver predictable performance and scale for well-structured access patterns.
Understanding these trade-offs is critical. MongoDB offers flexibility with minimal upfront planning, while DynamoDB rewards careful data modeling with predictable performance at scale.
Consistency, replication, and durability#
Modern applications require strong guarantees around data consistency, availability, and recovery — areas where both databases have improved significantly.
MongoDB offers tunable consistency levels, from strong to eventual, and supports automatic failover with replica sets. Atlas also provides multi-region writes, enabling higher availability and lower latency.
DynamoDB supports strongly consistent reads and eventual consistency, with automatic replication across availability zones. Global Tables v2 allows multi-region writes, reducing latency and enabling geo-distributed workloads.
Durability and fault tolerance are now comparable in both databases, but DynamoDB’s seamless integration with AWS’s infrastructure can offer a reliability advantage for existing AWS users.
Vector search and modern use cases#
The rise of AI and recommendation systems has made vector search a must-have feature for many applications. MongoDB now supports Atlas Vector Search, which integrates semantic search directly into the database. This allows you to store, index, and query embeddings alongside other document data.
DynamoDB doesn’t natively support vector search but can integrate with AWS OpenSearch or Amazon Kendra to provide similar functionality. For applications involving LLMs, personalized recommendations, or semantic queries, MongoDB has a clear edge thanks to its built-in support.
Data modeling, partitioning, and scaling guidance#
Data modeling is one of the most critical aspects of using any NoSQL database effectively. Both MongoDB and DynamoDB follow different philosophies:
MongoDB uses a flexible schema design that allows nested documents and arrays, making it easy to evolve your schema as requirements change.
DynamoDB, on the other hand, requires you to think in terms of access patterns upfront. Choosing a good partition key is essential to avoid hot partitions and performance bottlenecks.
Understanding these design principles early will save you from costly migrations and ensure optimal performance as your application scales.
Security, governance, and compliance#
Security has become a top priority in database design, and both platforms have strengthened their offerings:
MongoDB offers field-level encryption, role-based access control, auditing, and VPC peering. Atlas also provides compliance with GDPR, HIPAA, SOC 2, and other industry standards.
DynamoDB integrates tightly with AWS IAM for access control, supports encryption at rest and in transit, and provides VPC isolation and CloudTrail logging.
The differences are subtle but important. MongoDB offers more granular control over data governance, while DynamoDB benefits from deeper integration with AWS’s security ecosystem.
Real-world operational considerations#
Beyond features, real-world operations — such as migration, backup, and maintenance — are critical to your database choice.
Migration: MongoDB provides tools like mongomirror and Atlas Live Migration Service. DynamoDB can use AWS Database Migration Service (DMS) for migrating from SQL or NoSQL sources.
Backups and restores: Both databases now offer point-in-time recovery and automated backup solutions.
Monitoring and observability: Atlas integrates with tools like Prometheus and Datadog, while DynamoDB integrates with Amazon CloudWatch and AWS X-Ray.
Considering these operational aspects early can help you choose the database that best fits your team’s experience and infrastructure.