Response Streaming

Lambda Web Adapter supports Lambda response streaming, allowing your app to stream responses back to clients as they are generated.

Enabling Response Streaming

Set the invoke mode environment variable:

AWS_LWA_INVOKE_MODE=response_stream

This should match your Lambda Function URL's invoke mode configuration.

When to Use

Response streaming is useful for:

  • Server-sent events (SSE)
  • Large file downloads
  • Real-time data feeds
  • Reducing time-to-first-byte for slow-generating responses

Limitations

  • Compression (AWS_LWA_ENABLE_COMPRESSION) is not supported with response streaming. If both are enabled, compression is automatically disabled with a warning.
  • Response streaming works with Lambda Function URLs and API Gateway. ALB does not support streaming.

Examples