in our case the credentials were not specific for users rather for the lambda itself to operate against a DB instance. I would personally handle the develpercredentials differently.
Unfortunately the project grew over time and we did not start with a monorepo, so yes, we ended up with the credentials for each env shared by 3 different applications. that's why was handy to use SecretManager. 3 Secrets for 3 stages and no need to worry how many app will then use them. :-)
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