- Data model — documents (MongoDB) vs rows/tables (MySQL)
- Schema — flexible/dynamic vs fixed and enforced
- Joins — mostly avoided via embedding, or $lookup vs native SQL JOINs
- Scaling — horizontal sharding built-in vs traditionally vertical scaling
- Best fit — evolving/nested data vs strongly relational, transactional data
MongoDB vs MySQL
A document store with a flexible schema versus a relational database with fixed tables and strong join support.