What is Lambda Concurrency in AWS: Simple Explanation and Example
Lambda concurrency is the number of function instances that can run at the same time. It controls how many requests your Lambda function can handle simultaneously, helping manage performance and costs.How It Works
Imagine you have a bakery with several ovens. Each oven can bake one cake at a time. The number of ovens you have is like the concurrency for your Lambda function. If many customers order cakes at once, you can bake multiple cakes simultaneously, but only as many as you have ovens.
In AWS Lambda, concurrency means how many copies of your function can run at the same time to handle incoming requests. If your concurrency limit is 5, only 5 requests can be processed simultaneously; others wait or get throttled.
This helps control how your function scales and prevents overloading downstream resources like databases or APIs.
Example
This example shows how to set reserved concurrency for a Lambda function using AWS CLI. Reserved concurrency limits the maximum simultaneous executions.
aws lambda put-function-concurrency --function-name MyFunction --reserved-concurrent-executions 10
When to Use
Use Lambda concurrency settings when you want to control how many requests your function handles at once. This is useful to avoid overwhelming other services your function calls, like databases or APIs.
For example, if your function writes to a database that can only handle 20 writes per second, you can set concurrency to 20 to prevent errors.
Also, setting reserved concurrency guarantees your function always has capacity, which is important for critical tasks.
Key Points
- Concurrency means how many function instances run at the same time.
- Reserved concurrency sets a fixed limit to control scaling.
- Helps protect downstream resources from overload.
- Can guarantee capacity for important functions.