Error: DynamoDB Errors InvalidSignatureException Signature Expired

InvalidSignatureException: Signature expired means the request's signing timestamp is too old when AWS receives it. The usual causes are a clock that is out of sync or a signed request delayed or replayed after signing.

1. Compare the timestamp in the error with the machine's current UTC time. Check the host, VM or container environment that runs the client, not just your laptop.
2. Enable the operating system's automatic time synchronization. If a VM was suspended, verify its clock after resuming it. Containers normally share the host clock.
3. Retry through the SDK so it builds and signs a fresh request. Do not queue or replay a previously signed HTTP request.
4. If the time is correct, inspect application queues, connection saturation and proxies for delays between signing and sending.

date -u
aws sts get-caller-identity --profile app

Expired credentials are a separate problem: renew an SSO session or assumed-role credentials when the error is ExpiredToken or an invalid security token. Verify the signing Region and service if the message instead reports a credential-scope mismatch. Prefer a current AWS SDK credential provider over hand-written SigV4 signing, and keep credentials out of diagnostic logs.

See current JavaScript client examples and AWS documentation.