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        "title": "Choose Lambda reserved concurrency separately from preinitialized execution capacity",
        "summary": "A scaling ceiling and a latency preparation setting solve different operational problems.",
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        "potentially_affected": "This concerns the concurrency controls described for Lambda functions, with event-source-specific limits checked separately.",
        "dse_recommendation": "DSE recommends identifying whether the problem is downstream saturation, shared account capacity or initialization latency before changing a setting.",
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        "content_html": "<p>A scaling ceiling and a latency preparation setting solve different operational problems.</p>\n<h2>Source facts</h2>\n<p>Reserved concurrency sets an exclusive allocation and maximum concurrency for a Lambda function, reducing the pool available to other functions. Provisioned concurrency prepares execution environments and has separate charges. AWS documents reserved concurrency as a way to limit pressure on downstream resources; setting it to zero intentionally stops event processing.</p>\n<p>Source: <a href=\"https://docs.aws.amazon.com/lambda/latest/dg/configuration-concurrency.html\">AWS Documentation</a>.</p>\n<h2>Applicability</h2>\n<p>This concerns the concurrency controls described for Lambda functions, with event-source-specific limits checked separately.</p>\n<h2>DSE recommendation</h2>\n<p>DSE recommends identifying whether the problem is downstream saturation, shared account capacity or initialization latency before changing a setting. Measure representative request duration and traffic demand. Review the effect on other functions with the account owner and define acceptable throttling behavior. Keep a rollback value and an owner for queue or retry consequences. Do not treat reserved capacity as evidence that execution environments are already initialized for latency-sensitive work. Ask the downstream owner to approve the maximum simultaneous demand the function should generate. Record the desired outcome for throttled work and the observation that would justify a later increase, keeping a latency objective separate from the downstream-capacity decision.</p>\n<h2>Verification</h2>\n<p>Proposed verification: inspect the current concurrency configuration, run an approved bounded load against a test function and observe concurrency, throttles and downstream demand. Compare the result with the intended ceiling. Review provisioned-capacity needs separately and record the cost decision before enabling it.</p>\n<h2>Official reference</h2>\n<p><a href=\"https://docs.aws.amazon.com/lambda/latest/dg/configuration-concurrency.html\">AWS Documentation</a>. Reviewed October 20, 2026.</p>",
        "content_text": "A scaling ceiling and a latency preparation setting solve different operational problems.\nSource facts\nReserved concurrency sets an exclusive allocation and maximum concurrency for a Lambda function, reducing the pool available to other functions. Provisioned concurrency prepares execution environments and has separate charges. AWS documents reserved concurrency as a way to limit pressure on downstream resources; setting it to zero intentionally stops event processing.\nSource: AWS Documentation.\nApplicability\nThis concerns the concurrency controls described for Lambda functions, with event-source-specific limits checked separately.\nDSE recommendation\nDSE recommends identifying whether the problem is downstream saturation, shared account capacity or initialization latency before changing a setting. Measure representative request duration and traffic demand. Review the effect on other functions with the account owner and define acceptable throttling behavior. Keep a rollback value and an owner for queue or retry consequences. Do not treat reserved capacity as evidence that execution environments are already initialized for latency-sensitive work. Ask the downstream owner to approve the maximum simultaneous demand the function should generate. Record the desired outcome for throttled work and the observation that would justify a later increase, keeping a latency objective separate from the downstream-capacity decision.\nVerification\nProposed verification: inspect the current concurrency configuration, run an approved bounded load against a test function and observe concurrency, throttles and downstream demand. Compare the result with the intended ceiling. Review provisioned-capacity needs separately and record the cost decision before enabling it.\nOfficial reference\nAWS Documentation. Reviewed October 20, 2026.",
        "content_markdown": "A scaling ceiling and a latency preparation setting solve different operational problems.\n\n## Source facts\n\nReserved concurrency sets an exclusive allocation and maximum concurrency for a Lambda function, reducing the pool available to other functions. Provisioned concurrency prepares execution environments and has separate charges. AWS documents reserved concurrency as a way to limit pressure on downstream resources; setting it to zero intentionally stops event processing.\n\nSource: [AWS Documentation](https://docs.aws.amazon.com/lambda/latest/dg/configuration-concurrency.html).\n\n## Applicability\n\nThis concerns the concurrency controls described for Lambda functions, with event-source-specific limits checked separately.\n\n## DSE recommendation\n\nDSE recommends identifying whether the problem is downstream saturation, shared account capacity or initialization latency before changing a setting. Measure representative request duration and traffic demand. Review the effect on other functions with the account owner and define acceptable throttling behavior. Keep a rollback value and an owner for queue or retry consequences. Do not treat reserved capacity as evidence that execution environments are already initialized for latency-sensitive work. Ask the downstream owner to approve the maximum simultaneous demand the function should generate. Record the desired outcome for throttled work and the observation that would justify a later increase, keeping a latency objective separate from the downstream-capacity decision.\n\n## Verification\n\nProposed verification: inspect the current concurrency configuration, run an approved bounded load against a test function and observe concurrency, throttles and downstream demand. Compare the result with the intended ceiling. Review provisioned-capacity needs separately and record the cost decision before enabling it.\n\n## Official reference\n\n[AWS Documentation](https://docs.aws.amazon.com/lambda/latest/dg/configuration-concurrency.html). Reviewed October 20, 2026."
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