I think you can do the math yourself - the costs are published.
FYI - we did some experiments and the limiting factor was latency. 250-300ms on average, you have to go through their API feature as well, and that's part of the delay. But worse - Lamda's that have not been called for several minutes (I'm assuming they are not 'hot') often take several seconds, up to 5s to be called. So it creates a problem for intermittent traffic.
If that kind of latency is acceptable to you, it might work for you so long as the cost equation is right.
I think some other people had issues with versioning, it's a problem we didn't go far enough to observe.
Quick clarification: No need to go through API Gateway if you don't actually need the https endpoint - all AWS SDKs can hit Lambda's REST APIs directly, which also reduces p50 latency.
FYI - we did some experiments and the limiting factor was latency. 250-300ms on average, you have to go through their API feature as well, and that's part of the delay. But worse - Lamda's that have not been called for several minutes (I'm assuming they are not 'hot') often take several seconds, up to 5s to be called. So it creates a problem for intermittent traffic.
If that kind of latency is acceptable to you, it might work for you so long as the cost equation is right.
I think some other people had issues with versioning, it's a problem we didn't go far enough to observe.