Database Migration Guide
MongoDB Atlas to Amazon DocumentDB: Migration Guide and Comparison
An honest guide to MongoDB Atlas vs Amazon DocumentDB — covering compatibility gaps, migration steps with AWS DMS, cost comparison, and when each service is the right choice.
MongoDB Atlas to Amazon DocumentDB is one of the most nuanced database migrations you can undertake. On the surface it looks straightforward — DocumentDB speaks the MongoDB wire protocol, so your drivers connect. The complexity lives in the gaps between what DocumentDB advertises and what MongoDB actually delivers. This guide does not sugarcoat the compatibility story. We will cover what works, what does not, when DocumentDB is a reasonable choice, and when you should stay on Atlas or consider a different AWS-native option. We are an [AWS Select Tier Consulting Partner](/services/aws-migration), and we have handled Atlas-to-DocumentDB migrations. The advice here reflects production experience, not vendor documentation. ## The Compatibility Gap: What DocumentDB Does Not Support This is the section most vendor comparisons skip. Read it before you start planning a migration. | Feature | MongoDB Atlas | Amazon DocumentDB | Notes | | ------------------------ | ---------------------------------------------- | ------------------------------------------------------ | -------------------------------------------------- | | Full-text search | Atlas Search (Lucene-powered) | Not supported | Use Amazon OpenSearch Service alongside DocumentDB | | Change streams | Full support, collection + database level | Collection-level only, with restrictions | No db-level or deployment-level change streams | | $lookup (join) | Full support including uncorrelated subqueries | Partial — no uncorrelated subqueries | Rewrite complex joins before migrating | | $unionWith | Supported (MongoDB 4.4+) | Not supported | Requires application-level workaround | | $accumulator / $function | Supported | Not supported | Custom JS aggregation operators unavailable | | Time series collections | MongoDB 5.0+ | Not supported | Use Timestream or Redshift for time series | | MongoDB version | Tracks upstream releases | 4.0 and 5.0 wire protocol only | Does not receive MongoDB feature releases | | Transactions | Multi-document ACID | Single-region only; no cross-collection in all configs | Review transaction patterns carefully | | Atlas Vector Search | Supported | Not supported | Use Amazon OpenSearch with k-NN instead | | Atlas App Services | Supported | Not available | No DocumentDB equivalent | **The bottom line on compatibility:** For CRUD-heavy applications that do not use Atlas Search, complex aggregations, or change streams at the database level, DocumentDB's wire protocol compatibility is adequate. For applications that use these features, you are not migrating to DocumentDB — you are rewriting parts of your application. ## When DocumentDB Makes Sense DocumentDB is a reasonable choice in specific situations: - **AWS-only vendor requirement.** Some regulated environments or enterprise procurement policies require all data services to be native AWS services. Atlas runs on AWS infrastructure but is managed by MongoDB Inc., not AWS. DocumentDB satisfies this constraint. - **Operational simplicity over feature completeness.** If your team finds Atlas's operational model complex (cross-cloud replication, Atlas alerts, Atlas Data Federation), DocumentDB integrates more naturally into your existing AWS tooling — CloudWatch, VPC security groups, IAM authentication. - **Your workloads fit the compatibility matrix.** If your application is a document store for structured JSON with standard CRUD operations and simple queries, DocumentDB's supported feature set may be entirely sufficient. - **Cost modeling favors DocumentDB.** For low-I/O workloads, DocumentDB's unbundled pricing can be cheaper than Atlas. ## When Atlas Is the Better Choice Atlas is the stronger option when: - You use Atlas Search for full-text or relevance-based queries — there is no DocumentDB equivalent. The nearest AWS option is OpenSearch Service, which requires a separate migration. - You use Atlas Vector Search for semantic similarity search or RAG pipelines. - You use MongoDB 6.0 or later features. - Your application relies on change streams at the database or deployment level. - You use Atlas App Services, Atlas Data Federation, or Atlas Charts. - You need multi-cloud replication (Atlas runs on AWS, GCP, and Azure; DocumentDB is AWS-only). ## Cost Comparison DocumentDB uses an unbundled pricing model. The instance price is only part of the cost. | Tier | MongoDB Atlas | Amazon DocumentDB | Notes | | ------------------- | ------------------------------------- | -------------------------------------------------- | ------------------------------------------------------ | | Dev/shared | M0: Free, M2: $9/month, M5: $25/month | No free tier; minimum ~$43/month (db.t3.medium) | Atlas is dramatically cheaper for dev | | Entry production | M10: ~$57/month (2 vCPU, 2 GB) | db.t3.medium: ~$55/month + I/O ($20–100/month) | Comparable at this tier | | Standard production | M30: ~$169/month (2 vCPU, 8 GB) | db.r6g.large: ~$180/month + I/O ($50–200/month) | DocumentDB I/O can exceed instance cost | | Growth tier | M40: ~$325/month (4 vCPU, 16 GB) | db.r6g.xlarge: ~$360/month + I/O ($100–400/month) | DocumentDB becomes expensive for write-heavy workloads | | High performance | M60: ~$640/month (8 vCPU, 32 GB) | db.r6g.2xlarge: ~$720/month + I/O ($200–800/month) | I/O charges are the wildcard | **Critical caveat:** DocumentDB's I/O pricing ($0.20 per 1M IOs) can easily exceed the instance cost for write-heavy workloads. Always calculate worst-case I/O volume before committing to DocumentDB. ## Related Comparisons Explore other technical comparisons: - [DynamoDB vs RDS](/compare/dynamodb-vs-rds) ## Why Choose FactualMinds for Your AWS Migration FactualMinds is an **AWS Select Tier Consulting Partner** specializing in cloud platform migrations. We have executed GCP, DigitalOcean, Heroku, and MongoDB migrations to AWS and know the pitfalls. - **Migration architects** — assessment-first methodology mapping your current state before execution - **Zero-downtime cutover** — we execute migrations with minimal business impact - **AWS Select Tier Partner** — [verified on AWS Partner Network](https://partners.amazonaws.com/partners/001aq000008su2EAAQ/Factual%20Minds) - [AWS Marketplace Seller](https://aws.amazon.com/marketplace/seller-profile?id=seller-m753gfqftla7y) ---
MongoDB Atlas to Amazon DocumentDB is one of the most nuanced database migrations you can undertake. On the surface it looks straightforward — DocumentDB speaks the MongoDB wire protocol, so your drivers connect. The complexity lives in the gaps between what DocumentDB advertises and what MongoDB actually delivers.
This guide does not sugarcoat the compatibility story. We will cover what works, what does not, when DocumentDB is a reasonable choice, and when you should stay on Atlas or consider a different AWS-native option.
We are an AWS Select Tier Consulting Partner, and we have handled Atlas-to-DocumentDB migrations. The advice here reflects production experience, not vendor documentation.
The Compatibility Gap: What DocumentDB Does Not Support
This is the section most vendor comparisons skip. Read it before you start planning a migration.
| Feature | MongoDB Atlas | Amazon DocumentDB | Notes |
|---|---|---|---|
| Full-text search | Atlas Search (Lucene-powered) | Not supported | Use Amazon OpenSearch Service alongside DocumentDB |
| Change streams | Full support, collection + database level | Collection-level only, with restrictions | No db-level or deployment-level change streams |
| $lookup (join) | Full support including uncorrelated subqueries | Partial — no uncorrelated subqueries | Rewrite complex joins before migrating |
| $unionWith | Supported (MongoDB 4.4+) | Not supported | Requires application-level workaround |
| $accumulator / $function | Supported | Not supported | Custom JS aggregation operators unavailable |
| Time series collections | MongoDB 5.0+ | Not supported | Use Timestream or Redshift for time series |
| MongoDB version | Tracks upstream releases | 4.0 and 5.0 wire protocol only | Does not receive MongoDB feature releases |
| Transactions | Multi-document ACID | Single-region only; no cross-collection in all configs | Review transaction patterns carefully |
| Atlas Vector Search | Supported | Not supported | Use Amazon OpenSearch with k-NN instead |
| Atlas App Services | Supported | Not available | No DocumentDB equivalent |
The bottom line on compatibility: For CRUD-heavy applications that do not use Atlas Search, complex aggregations, or change streams at the database level, DocumentDB’s wire protocol compatibility is adequate. For applications that use these features, you are not migrating to DocumentDB — you are rewriting parts of your application.
When DocumentDB Makes Sense
DocumentDB is a reasonable choice in specific situations:
- AWS-only vendor requirement. Some regulated environments or enterprise procurement policies require all data services to be native AWS services. Atlas runs on AWS infrastructure but is managed by MongoDB Inc., not AWS. DocumentDB satisfies this constraint.
- Operational simplicity over feature completeness. If your team finds Atlas’s operational model complex (cross-cloud replication, Atlas alerts, Atlas Data Federation), DocumentDB integrates more naturally into your existing AWS tooling — CloudWatch, VPC security groups, IAM authentication.
- Your workloads fit the compatibility matrix. If your application is a document store for structured JSON with standard CRUD operations and simple queries, DocumentDB’s supported feature set may be entirely sufficient.
- Cost modeling favors DocumentDB. For low-I/O workloads, DocumentDB’s unbundled pricing can be cheaper than Atlas.
When Atlas Is the Better Choice
Atlas is the stronger option when:
- You use Atlas Search for full-text or relevance-based queries — there is no DocumentDB equivalent. The nearest AWS option is OpenSearch Service, which requires a separate migration.
- You use Atlas Vector Search for semantic similarity search or RAG pipelines.
- You use MongoDB 6.0 or later features.
- Your application relies on change streams at the database or deployment level.
- You use Atlas App Services, Atlas Data Federation, or Atlas Charts.
- You need multi-cloud replication (Atlas runs on AWS, GCP, and Azure; DocumentDB is AWS-only).
Cost Comparison
DocumentDB uses an unbundled pricing model. The instance price is only part of the cost.
| Tier | MongoDB Atlas | Amazon DocumentDB | Notes |
|---|---|---|---|
| Dev/shared | M0: Free, M2: $9/month, M5: $25/month | No free tier; minimum ~$43/month (db.t3.medium) | Atlas is dramatically cheaper for dev |
| Entry production | M10: ~$57/month (2 vCPU, 2 GB) | db.t3.medium: ~$55/month + I/O ($20–100/month) | Comparable at this tier |
| Standard production | M30: ~$169/month (2 vCPU, 8 GB) | db.r6g.large: ~$180/month + I/O ($50–200/month) | DocumentDB I/O can exceed instance cost |
| Growth tier | M40: ~$325/month (4 vCPU, 16 GB) | db.r6g.xlarge: ~$360/month + I/O ($100–400/month) | DocumentDB becomes expensive for write-heavy workloads |
| High performance | M60: ~$640/month (8 vCPU, 32 GB) | db.r6g.2xlarge: ~$720/month + I/O ($200–800/month) | I/O charges are the wildcard |
Critical caveat: DocumentDB’s I/O pricing ($0.20 per 1M IOs) can easily exceed the instance cost for write-heavy workloads. Always calculate worst-case I/O volume before committing to DocumentDB.
Related Comparisons
Explore other technical comparisons:
Why Choose FactualMinds for Your AWS Migration
FactualMinds is an AWS Select Tier Consulting Partner specializing in cloud platform migrations. We have executed GCP, DigitalOcean, Heroku, and MongoDB migrations to AWS and know the pitfalls.
- Migration architects — assessment-first methodology mapping your current state before execution
- Zero-downtime cutover — we execute migrations with minimal business impact
- AWS Select Tier Partner — verified on AWS Partner Network
- AWS Marketplace Seller
Frequently Asked Questions
Is Amazon DocumentDB the same as MongoDB?
No. Amazon DocumentDB implements a subset of the MongoDB 4.0 and 5.0 wire protocol, which means most MongoDB drivers and tools can connect to it. However, DocumentDB is a purpose-built AWS service — not MongoDB under the hood. It has documented gaps: limited change streams, partial $lookup support, no full-text search (use Amazon OpenSearch instead), and missing aggregation pipeline operators. For simple CRUD-heavy workloads the compatibility is sufficient; for feature-intensive applications it is not.
Can I migrate from MongoDB Atlas to DocumentDB?
Yes. The recommended path is AWS Database Migration Service (DMS), which supports MongoDB as a source and DocumentDB as a target. Before committing to the migration, audit your application code for any aggregation operators, change stream usage, or text search queries — these may need reworking. Run the DocumentDB compatibility checker on your queries before you start.
What are the limitations of Amazon DocumentDB?
The most significant limitations: no full-text search (Atlas Search uses Lucene; DocumentDB has none — use Amazon OpenSearch alongside DocumentDB instead), limited change stream support (only available at the collection level with restrictions), partial $lookup (no uncorrelated subqueries), and missing aggregation operators including $unionWith, $accumulator, and $function. DocumentDB also lags behind MongoDB version releases — it supports MongoDB 4.0 and 5.0 wire protocols but does not track upstream MongoDB feature releases.
Is DocumentDB cheaper than MongoDB Atlas?
It depends on your I/O patterns. DocumentDB uses an unbundled pricing model: you pay separately for instance hours, storage ($0.10/GB-month), and I/Os ($0.20/million). Atlas bundles everything into the instance price. At low I/O volumes, DocumentDB can be cheaper. At high I/O volumes (write-heavy workloads), the per-I/O charges can exceed Atlas pricing. Always model your expected I/O before assuming DocumentDB is cheaper.
Does DocumentDB support MongoDB 5.0?
DocumentDB supports the MongoDB 5.0 wire protocol for compatibility purposes, but this does not mean it supports all MongoDB 5.0 features. Specific 5.0 features like time series collections and window functions in aggregation pipelines are not available in DocumentDB. Check the AWS DocumentDB compatibility matrix for the specific features your application uses before migrating.
Ready to Migrate to AWS?
FactualMinds is an AWS Select Tier Consulting Partner. We run assessment-first migrations — mapping your current architecture, estimating risk, and executing with zero-downtime cutover strategies.