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DVA-C03 practice question: Concurrency and performance tuning (1 of 3)

Troubleshooting and Optimization A free question from our original DVA-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.

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An online ticketing API runs a Node.js Lambda function behind Amazon API Gateway.

Demand jumps every weekday at 09:00, and users must see consistently low latency from the first request, without paying for that capacity all day. The API calls the function through an alias named live, which points to a published version.

What should the developer configure?

Choose one answer.

  1. A. Provisioned concurrency set on $LATEST, with a scheduled scaling action that raises it at 08:45 each weekday.
  2. B. Reserved concurrency set to the expected 09:00 peak, so that enough environments exist for the burst.
  3. C. Provisioned concurrency on the live alias, raised by a scheduled action before 09:00 and lowered afterwards.
  4. D. SnapStart turned on for the function, since it removes cold starts for every invocation.
Show the answer and explanation

Answer: C

  • A. Wrong: Provisioned concurrency cannot be set on $LATEST, only on a published version or an alias. The schedule would never take effect on the function the API calls.
  • B. Wrong: Reserved concurrency limits how many environments a function can use, and it does not start any in advance. The first requests at 09:00 would still hit cold starts.
  • C. Right: Correct. Provisioned concurrency keeps environments initialized on a published version or an alias, so requests skip the cold start. Application Auto Scaling can schedule a higher level before the peak and a lower one afterwards. Learn more: Configuring provisioned concurrency for a function (opens in a new tab)
  • D. Wrong: SnapStart supports Java, Python and .NET runtimes, not Node.js. It also reduces startup time without guaranteeing low latency for every request.

Explanation

Provisioned concurrency pre-initializes execution environments for a published version or alias, and a scheduled action can raise it before a predictable peak. Reserved concurrency only limits capacity. SnapStart does not support Node.js, and it is not a guaranteed cold-start fix.

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