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X: what's your opinion on VTL templates vs direct lambda invocations with AppSync?
me: you should use VTL templates (e.g. for DynamoDB) by default until it's either impossible or the VTL is getting too complex
X: but why?
me: well, let's see..
me: you should use VTL templates (e.g. for DynamoDB) by default until it's either impossible or the VTL is getting too complex
X: but why?
me: well, let's see..
me: you can do whatever you want with Lambda, that gives you a lot of flexibility, but also all the drawbacks
X: such as?
me: cold starts, esp for resolvers that don't see a lot of traffic or the complexity overhead for mitigating them (Provisioned Concurrency or lambda warmer)
X: such as?
me: cold starts, esp for resolvers that don't see a lot of traffic or the complexity overhead for mitigating them (Provisioned Concurrency or lambda warmer)
me: and you also have to consider the operational limits specific to Lambda, such as the *soft regional concurrency limit, and the *hard limit of 500 new concurrent executions per min after the init burst capacity (3000 concurrent executions)
X: ok, fair point.. anything else?
X: ok, fair point.. anything else?
me: yes, there's also the extra cost for invoking the Lambda function, plus the cost for monitoring that function (e.g. CW Logs and X-Ray)
X: aren't there any other upside for using Lambda?
me: there is, actually!
X: aren't there any other upside for using Lambda?
me: there is, actually!
me: the AWS SDKs give you retry & exponential backoff OOTB; you can implement fall-back & circuit breakers to make your app more resilient to failures; you can do failure injection to proactively identity failure modes in your app
X: but you'd still prefer VTL by default?
X: but you'd still prefer VTL by default?
me: yes!
X: why..?
me: because simplicity wins and most of the time good enough is good enough
You should start with the simplest solution and make it more complex when you need to, not the other way around
X: why..?
me: because simplicity wins and most of the time good enough is good enough
You should start with the simplest solution and make it more complex when you need to, not the other way around
