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Cap a Function with Reserved Concurrency

A 3-step recipe with AWS Lambda. We can help you get access.

Recipe · 3 steps

Cap a Function with Reserved Concurrency

with AWS Lambda

Set and verify the maximum simultaneous executions reserved for a function.

  1. Read the existing reservation before changing it, so the prior value is captured for audit and rollback. A function with no reservation returns no ReservedConcurrentExecutions value and draws from the shared account pool.
  2. Set the ceiling. This carves the reserved amount out of the account's regional concurrency pool, so the capacity is no longer available to any other function in the account.
  3. Read the reservation back to confirm the ceiling Lambda actually stored matches what was requested.
What you'll need to have ready
  • functionName: The name or ARN of the function to cap.
  • reservedConcurrentExecutions: Maximum simultaneous executions for this function. Setting 0 stops the function from being invoked at all, which is the standard way to quarantine a misbehaving
For your developer

Arazzo workflow aws-lambda:reserved-concurrency-guardrail, 3 operations: getReservedConcurrency → PutFunctionConcurrency → getReservedConcurrency. Specs on APIs.io.

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