Keep a busy function from flooding a database — Lambda and Concurrency

Your goal

Set and inspect a ceiling on overlapping function runs.

Why this matters

Too many function runs at once can overwhelm a downstream service. Reserved concurrency places a bound on overlap for a function. You will save a small limit and read it back.

Words you will use

Concurrency means runs happening at the same time. Reserved concurrency sets aside capacity for a function and caps its simultaneous runs.

How to proceed

Start a fresh emulator, read each numbered step, and enter the practice settings shown. Run the action, inspect its API receipt, then continue. Finish lab checks the emulator state again before saving your progress.

1. Create your practice function

Create a Lambda function using the site’s fixed practice handler. Wait for its state to become Active. Your function has its own name and role in this emulator.

2. Set reserved concurrency

Enter a maximum number of simultaneous runs. Reserved concurrency sets aside capacity and also imposes a ceiling. This configuration lab does not run a load test.

Reserved concurrency: Choose 1–20 overlapping runs for the practice setting. Suggested practice value: 5.

3. Read the function setting

Retrieve the setting from the emulator and compare it with your input. The returned state is the evidence used to complete this lab.

Practice, then check your understanding

Perform the actions yourself and inspect the returned state. Errors keep your settings so you can retry. Starting another lab clears the previous live environment. Earned XP is kept, and signed-in achievements sync to your account. Replay does not award duplicate XP.

Read the official AWS documentation for service behavior and production details.