-
Hello Klimok,
Great question. I remember wondering about this a lot beforehand when I was studying them. Honestly, it’s all about limits and objectives. Here are some observations we noticed during our experience with the exams:
1) MongoDB compatibility. DocumentDB was launched back in early 2019 to accommodate the customers who want to migrate their on-premise MongoDB database. (e.g. heavy reliance of MongoDB APIs).
2) DocumentDB nesting – 100 levels & DynamoDB nesting depth – 32 levels
3) DynamoDB indexes – 5 LSI, 20 GSI; DocumentDB – 64 per collection
4) How the Shared Responsibility Model works with DynamoDB vs DocumentDB – DynamoDB is great for serverless architecture. DocumentDB is instance-based. DynamoDB is a fully-managed service while DocumentDB requires some administrative tasks (which may be desirable if you still want to have a feel that resembles that of traditional database management).
There should be more, but this may be enough for the exam. I suggest you read more on the limits pages, too. Jon may have other ideas (e.g. security or networking)
Hope this helps.
Joboy
