Doesn't something like localstack.cloud help with this need? I've just recently inherited some NodeJS lambdas and am thinking of looking into that to debug/develop locally.
LocalStack is great tool but the difference here is that MerLoc runs your function in local against real cloud services with the same credentials of your real AWS Lambda function. So there is no AWS service simulation, mocking or local implementation here.
Not exactly. The paid editions have free trials, but there's also a community edition that is free. However, it's pretty difficult to figure out what exactly is supported in the community edition. There's a whole list that mention various AWS services are only supported in "PRO", but I don't know if that means that free support might come later in community.
[Disclaimer] I am the co-founder and CTO at Thundra which is serverless monitoring and debugging solution.
We also have developed another debugging tool to debug AWS Lambda function on remote AWS Lambda environment from your local IDE: https://www.serverlessdebugger.com/
It doesn't support hot-reload but very useful for debugging functions.