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MongoDB Best Practices
Opens with creditsA practical guide to MongoDB best practices for application developers. It covers supported versions, schema design around access patterns, schema validation including the new constraint level in 9.0, compound indexes with the ESR guideline, queries and aggregation within memory limits, write concern and transactions, driver connection handling, and the security checklist for a production deployment.
Written by Tauseef Fayyaz8 chapters, 30 practicesAbout 19 min29 quiz questionsReviewed 13 October 2026What you will learn
8 chapters · about 19 min
1Versions and deploymentWhich MongoDB versions are supported, why every deployment should be a replica set, and how to approach a major upgrade.3 practices · 2 min
2Schema designDesigning documents around how the application reads and writes data, and avoiding the anti-patterns the MongoDB docs call out.5 practices · 3 min
- Schema validationLetting the database reject malformed documents, and rolling validation out safely on collections that already have data.3 practices · 2 minOpens with credits
- IndexingBuilding compound indexes in the right field order, checking them with explain, and keeping the index set lean.4 practices · 3 minOpens with credits
- Queries and aggregationReading only what you need, paginating efficiently and keeping aggregation pipelines within MongoDB 9.0 memory limits.4 practices · 2 minOpens with credits
- Writes, consistency and transactionsChoosing write and read concern, designing for single-document atomicity, and using multi-document transactions within their limits.4 practices · 3 minOpens with credits
- Drivers and connectionsCreating and reusing clients, setting timeouts and handling serverless platforms without exhausting connections.3 practices · 2 minOpens with credits
- Security and operationsThe MongoDB security checklist applied to a typical application, plus backups and monitoring.4 practices · 2 minOpens with credits
About this guide
MongoDB best practices start from one idea in the MongoDB docs: data that is accessed together should be stored together. A flexible schema does not mean no schema. It means the schema follows your queries instead of a normalised diagram, and that choice is yours to make deliberately. Get it wrong and you end up with arrays that grow until documents hit the size limit, $lookup chains that rebuild joins badly, or collections with dozens of indexes that slow every write.
This guide starts with versions, then goes through modelling documents around access patterns, enforcing structure with schema validation, designing compound indexes with the Equality, Sort, Range guideline, writing queries and aggregations that stay within memory limits, choosing write concern and using transactions sparingly, handling driver connections, and securing and operating a deployment.
Everything here was checked against the MongoDB manual and lifecycle pages as of October 2026. MongoDB 9.0 was released in September 2026 (latest patch 9.0.2), and MongoDB 8.0 remains supported until October 2029. Where 9.0 changes behaviour, such as per-query memory limits, the constraint validation level and a cap on open transactions, the practice says so.
Common questions
What is the latest version of MongoDB?
MongoDB 9.0 was released in September 2026, with 9.0.2 as the latest patch at the time of writing. MongoDB 8.0 is supported until October 31, 2029 and 7.0 until August 31, 2027. Check the MongoDB lifecycle schedules page for current dates.
Should I embed or reference documents in MongoDB?
Embed data that is read together with its parent and stays small and bounded. Reference data that grows without limit, is shared by many parents or is often read on its own. Many schemas embed a small recent subset and reference the full history.
What is the ESR rule for MongoDB indexes?
It is the order for compound index fields: Equality fields first, then Sort fields, then Range fields. Following it lets one index filter and sort efficiently. If a range filter is very selective, putting it before the sort can be better.
Does MongoDB support transactions?
Yes, multi-document ACID transactions on replica sets and sharded clusters. Keep them short, since they abort after 60 seconds by default, and use the driver withTransaction helper for correct retries. Design the schema so most operations only need single-document atomicity.
What is the maximum document size in MongoDB?
A BSON document can be at most 16 MiB, with up to 100 levels of nesting. Larger files belong in GridFS or object storage. Arrays that grow without bound are the usual way documents approach the limit.
Does MongoDB need a schema?
It does not require one, but production apps benefit from one. Design documents around access patterns, then use $jsonSchema validation to enforce required fields and types so every writer follows the same rules.
Sources (8)
Checked against these, last on 13 October 2026.
- MongoDB Software Lifecycle Schedules, MongoDBwww.mongodb.com/legal/support-policy/lifecycles
- Release Notes for MongoDB 9.0, MongoDB docswww.mongodb.com/docs/manual/release-notes/9.0/
- Data Modeling, MongoDB docswww.mongodb.com/docs/manual/data-modeling/
- Schema Design Anti-Patterns, MongoDB docswww.mongodb.com/docs/manual/data-modeling/design-antipatterns/
- The ESR (Equality, Sort, Range) Guideline, MongoDB docswww.mongodb.com/docs/manual/tutorial/equality-sort-range-guideline/
- Production Considerations (Transactions), MongoDB docswww.mongodb.com/docs/manual/core/transactions-production-consideration/
- Security Checklist for Self-Managed Deployments, MongoDB docswww.mongodb.com/docs/manual/administration/security-checklist/
- MongoDB Limits and Thresholds, MongoDB docswww.mongodb.com/docs/manual/reference/limits/
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