Designing Idempotent APIs

Links: 300 home

Designing Idempotent APIs¶

An idempotent request is a request that you can be retried multiple times without having side effects in the backend.
- For example GET is always an idempotent method.
- No matter how many GET calls you make it is not going to change anything.

We want to have resiliency in our APIs i.e. if something goes wrong it automatically recovers from failures.
To achieve this we use different retry mechanisms like exponential backoff.

So what is the problem of retries for non idempotent APIs?

Potential problem of no response back to the client from the backend due to a network issue but request was sent to the database by the backend and an entry was created.
We might end up with multiple entries with the same data incase of retries from the client.

Passing the input arguments of the request through a hash function and storing the output in a database and then comparing the subsequent requests with the hash.
- One con of doing it this way is that if you wanted to create 2 resources of the same kind intentionally you wouldn't be able to do it.
Another way of doing it is that the client generates a unique token and uses it for the request or any other subsequent retries.
- We can mitigate the above con using this approach since we would be generating a new token for creating another resource.
- One important thing is that we need to return syntactically identical response.

Last updated: 2023-01-30