AWS Bedrock Error: 'Task timed out after X seconds' (AWS Lambda in Bedrock)
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A diagnostic guide to resolving AWS Bedrock failures caused by AWS Lambda execution time limits.
Problem
An AWS Lambda function invoking AWS Bedrock fails with a timeout error.
Typical error:
Task timed out after X.XX seconds
Common symptoms:
- Lambda logs show the timeout message
- No Bedrock response is returned
- Inference may start but never completes
- The same code works outside Lambda or with smaller inputs
The function is forcibly terminated by Lambda.
Clarifying the Issue
This is not an IAM issue.
This is not an SDK or client mismatch issue.
📌 This error occurs when AWS Lambda reaches its maximum execution time before Bedrock inference completes.
📌 The compute environment stops the process—even if Bedrock is still working.
Why It Matters
This failure is common when:
- Lambda timeout is left at the default (3 seconds)
- Prompts or outputs grow over time
- Larger or slower models are introduced
- Streaming responses are not handled correctly
- Lambda is used for synchronous inference without tuning
Lambda is optimized for short-lived execution, not long-running inference by default.
Key Terms
- Lambda timeout – Maximum execution duration (default: 3s, max: 15m)
- Execution environment – The Lambda runtime container
- Cold start – Startup latency before code runs
- Inference latency – Time spent generating model output
- Streaming – Incremental response delivery
Steps at a Glance
- Confirm the error is a Lambda task timeout
- Check the configured Lambda timeout
- Evaluate inference duration and payload size
- Adjust architecture or execution model
- Retest the invocation
Detailed Steps
1. Confirm the Timeout Source
Verify the error message explicitly states:
Task timed out after X seconds
📌 This indicates Lambda, not the SDK or network, terminated execution.
2. Check Lambda Timeout Configuration
Default Lambda timeout is 3 seconds.
Increase it as needed:
- Lambda → Configuration → General
- Set timeout based on inference duration
Guidance:
- Small prompts: 10–30 seconds
- Medium prompts: 1–2 minutes
- Large prompts or streaming: 3–5 minutes
If Lambda times out, the Bedrock response is lost.
3. Evaluate Inference Duration and Payload Size
Long-running inference is often caused by:
- Large prompts
- Long conversation history
- High
max_tokenssettings - Large documents passed inline
Mitigations:
- Reduce prompt size
- Chunk or summarize inputs
- Lower output token limits
- Offload preprocessing upstream
Inference time scales with token volume.
4. Review Streaming vs Non-Streaming Usage
Streaming can reduce perceived latency, but:
- Lambda must actively consume the stream
- Blocking on full output negates streaming benefits
- Improper handling can still hit the timeout
Ensure streamed responses are processed incrementally.
5. Consider Architectural Alternatives
If inference regularly exceeds Lambda limits:
- Use asynchronous workflows
- Trigger inference via Step Functions
- Offload to ECS or EC2 for long-running jobs
- Use Lambda only as an orchestration layer
Lambda is not always the right execution model for inference.
6. Retest the Invocation
After adjusting:
- Lambda timeout
- Payload size
- Streaming handling
- Execution architecture
Retry the invocation.
If it succeeds, the root cause was Lambda execution limits, not Bedrock availability.
Pro Tips
- Lambda defaults are not inference-friendly
- Cold starts add overhead to tight time budgets
- Streaming helps responsiveness but not total runtime
- Long inference belongs outside synchronous Lambda
- Timeout errors are compute failures, not service failures
Conclusion
The error:
Task timed out after X seconds
means that AWS Lambda terminated execution before Bedrock finished responding.
Once:
- Lambda timeout is increased
- Payload size is controlled
- Streaming is handled correctly
- Architecture matches inference duration
AWS Bedrock invocation completes successfully.
Increase the timeout.
Reduce the payload.
Change the execution model if needed.
Aaron Rose is a software engineer and technology writer at tech-reader.blog and the author of Think Like a Genius.
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