Lambda contract

Confirm before relying. Quotas, prices, and names change.

Lambda is a seam, not a place to hide a CRM

Synchronous invoke waits at most 8 seconds. Asynchronous mode can be paired with a Wait of up to 60 seconds. A chain of Lambda calls in one contact must stay within 20 seconds.

Connect retries throttles and HTTP 500s, up to three times, until the block timeout. Your function should be safe to run twice.

• Add the function to the instance. An identity policy alone does not let the flow invoke it.
• Return a flat string map or JSON, matching the block. Nested objects fail a string-map block.
• Log the ContactId. The flow log has no Lambda RequestId to join on.
• Default block timeout is 3 seconds. Raise it on purpose, not by hoping.

Source: Lambda function block

The response contract

Match the block's response validation. A string map is a flat object of strings. JSON validation allows nested JSON. The re:Post guidance says to keep the payload small, with 32 KB as the figure people hit, and to restrict values to characters Connect accepts when you are on a string map.

Print the ContactId. Correlate by time only if you forgot.

• Idempotent writes. Retries happen.
• Timeouts in the Lambda console must be higher than the block timeout or you will add a second failure mode.
• Cold starts count against the 8 seconds.
• Secrets stay in the function environment or in Secrets Manager, not in flow attributes.

Source: re:Post, Lambda failures