A practical guide to implementing the CQRS (Command Query Responsibility Segregation) pattern in Java using Spring Boot and MongoDB. Covers creating separate read and write repositories (ItemReadRepository and ItemWriteRepository), using MongoTemplate for precise write operations, and why Spring's save()/saveAll() methods should be avoided. Explains the performance and operational risks of full-document replacement, including increased network traffic and MongoDB oplog bloat, and shows how targeted $set updates are preferable.
Table of contents
The Spring standard repositoryCreating separate repositories for the read and writeWhen requirements changeThe double-edged sword of Spring updates in MongoDBConclusionSort: