A Lambda function runs a handler when an event invokes it. Node and Python use different source syntax and handler conventions, but both receive event data and produce a result or an error. The execution role supplies permissions to call other services; the handler name doesn't grant them.
Execution settings affect behavior. A timeout ends an invocation that exceeds its allowed duration, while memory also influences available compute. Test normal, missing, and invalid inputs before assuming a successful invocation covers every event. This simulator runs supported Node or Python handlers in a local worker and reports the output. It doesn't contact AWS. A timeout can be a symptom of a slow dependency, a blocked network path, or a retry problem, so read logs before simply raising the number.