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Sabarish Sathasivan
Sabarish Sathasivan

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AWS Serverless Payload Limits Expand to 1 MB: What It Means for Event-Driven Architectures

#architecture #serverless #eventdriven #aws

AWS has been steadily increasing the maximum payload size from 256 KB to 1 MB across key serverless services. This is a meaningful improvement for event-driven architectures that rely on richer event data and reduced fragmentation.

Modern cloud applications no longer pass around small strings or simple messages. LLM prompts, telemetry signals, personalization context, ML outputs, and user interaction data are often nested JSON objects carrying real state and meaning. Until recently, fitting this data into serverless workflows required careful design tradeoffs.

Recent Announcements

AWS first introduced the 1 MB payload limit for individual services:

1 MB Limit for Event-Driven Lambda

With the announcement - More room to build: serverless services now support payloads up to 1 MB on January 29, 2026, AWS confirmed that the 1 MB payload size limit now applies consistently to asynchronous Lambda invocations originating from Amazon SQS and Amazon Event Bus in Amazon EventBridge also.

This removes the need for several common architectural workarounds, such as:

  • Chunking large payloads into multiple events
  • S3 Claim Check Pattern - Storing payloads in Amazon S3 and passing object references in the event
  • Compressing data to fit within size limits

Considerations

  • Lambda memory and performance
    Since parsing larger JSON payloads can increase both memory consumption and execution time, especially in high-throughput event-driven workloads.

  • Lambda timeouts still apply
    The payload size may now be 1 MB, but Lambda timeouts (up to 15 minutes) and memory limits remain unchanged and should factor into your design decisions.

  • S3 Claim Check Pattern still matter
    Storing large payloads in Amazon S3 and passing lightweight references through events remains a good choice when data exceeds size limits, is shared across consumers, or requires strong governance and traceability.

  • The Messaging Cost (SQS & EventBridge)
    While payload limits have increased, billing is still based on 64 KB chunks. Both Amazon SQS and Amazon EventBridge meter usage per 64 KB unit. As a result, a single 1 MB (1,024 KB) event is billed as 16 requests, not one. In high-volume systems, this can significantly increase messaging costs.

  • The Compute Cost (Lambda Async)
    For async Lambda invocations, the first 256 KB is billed as one request, with an additional request charged for every 64 KB beyond that. This means a 1 MB (1024 KB) async event is billed as 13 requests (1 base + 12 additional chunks). At scale, these hidden request multipliers can quickly erode your compute budget.

This table provides a quick reference for calculating the real cost of your payloads.

Payload Size Billable Requests (SQS / EventBridge) Billable Requests (Lambda Async)
Up to 64 KB 1 1
256 KB 4 (4 *64 KB) 1 (1*256 KB)
512 KB 8 (8 * 64 KB) 5 (1 * 256 KB + 4 * 64 KB)
1 MB (1024 KB) 16 (16 * 64 KB) 13 (1 * 256 KB + 12 * 64 KB)

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