Comment by Mohit Yadav on "How to model relational data in DynamoDB"

CommentHow to model relational data in DynamoDB

Mohit Yadav

I Live to create better apps everyday

Mar 20, 2022

Great to learn something! I'm new to DynamoDB and still confused why you prepended project# and monitor# to some GSIs, this would increase the redundancy and also unintentionally increase storage space.

Also, while querying, why do you query both, the primary key and the GSI, even though the schema says they contain the same data.

I might be totally getting the concept of GSIs wrong. Pardon me for that.

Thanks for the awesome and in-depth article 🎉

Stefan Olaru

Head of Development | Architect | 7x AWS Certified | AWS Community Builder | Serverless

Mar 21, 2022

Hey Mohit Yadav, good question.

It's called index overloading. The table can hold many different kinds of data items at one time, hence we use generic names for primary key (PK), sort key (SK), and global secondary index (GSI).

Prefixing allows to identify the entity to be queried, e.g. user-related items will always have PK starting with user#, so on.

We can get the project details using GetItem, but to Query all projects of an org we'll have to use the overloaded GSI like GSI=org#1234 AND begins_with(SK, project#).

Thanks for the in-depth answer, Stefan!

Honestly speaking, I understand most of this, but some concepts are still a bit rusty... Explaining them may be out of the scope of this article, so I'll definitely learn them when I get into NoSQL DBs. 😃

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