Concurrency

Concurrency can mean different things depending on the context.

In local rendering, concurrency refers to how many browser tabs are opened in parallel during a render.
Each Chrome tab renders web content and then screenshots it.

For rendering on Lambda, concurrency refers to the number of chunks that can be rendered in parallel. Normally, each chunk is handled by a separate Lambda function. You can control the Lambda concurrency using the framesPerLambda option.

From v4.0.517, you can set concurrency to 1 to render the video on the main function.

Each Lambda function usually opens just a single tab, unless you use the concurrencyPerLambda option to increase the amount of tabs per Lambda function.

Higher concurrency can lead to faster render times, but too high concurrency will lead to diminishing returns and to overload of the machines, which might crash a render.