Can an AWS Lambda modify a json file on itself?

Question

I have an AWS Lambda function. which have an array on a .json file. now the thing is that I want to modify that .json but after the run, the json remains exactly the same than before the run. The logs I place there make me think that is actually being modified, but, I wonder if a lambda goes back to its definition before the run. tbh the information that I need to hold in that json is going to be always just a small amount of settings but those are going to be easy to modify without making a deploy and im trying to avoid using a db or an s3 bucket.

Regards, Daniel

Answer 1

You're not going to be able to do this. Lambda stores the deployment package (i.e. the .zip or .jar file you used to deploy) and uses that package for the next Lambda it spins up. This new Lambda may or may not be the one that just ran.

The easiest way will be to store this in an S3 bucket. Be aware though that just like in multi-threaded programming you may have many processes (Lambda instances) running at the same time so resource contention is something to be aware of.

Answer 2

I want you to consider the following behaviour of Lambda function:

Let's say you spin one lambda up , and then you send a second message to lambda .

If you first lambda finished before you send the second message

The same lambda will run the message .

So this is why you see it changed the file , it's on the same instance with same files .

I would suggest loading json into memory , and not change the file directly .

That will solve your problem.