I want to process events from an SNS topic using a lambda function and to keep cost down I don’t want to have an SQS queue in between.

I also don’t want to lose any events e.g. due to throttling so I’m thinking of having a DLQ for discarded events.

Is it true that an event using this setup will either be successfully handled by the lambda or put on the DLQ? Or are there cases when events could be lost e.g. due to high request rates?

This sentence from the documentation seems to support the latter but I’m not sure:

If the function can’t keep up with incoming events, events might also be deleted from the queue without being sent to the function.