Dynamo vs Document DB

[Klimok]

Hi Jon’s team,

In your and Stephane Maarek’s questions sets if you’re down to choosing between Dynamo and Doc, normally Doc is disqualified because of no global or no DAX support. But what will be the situation when Doc will be preferred over Dynamo?

[Joboy-Pineda-TD]

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

[Klimok]

Hi Joboy,

I actually found 1 question in your 2nd exam set. It’s about the max size of the item – 400k DDB vs 16MB DocDB. Also DocDB is a regional service while DDB can be global.

[tommylee9595]

https://docs.aws.amazon.com/documentdb/latest/developerguide/global-clusters.html

According to this, you could have a global DB. however it’s not multi-master (aka multi-writer) so it’s probably important to read if the question has that requirement