Understanding Edge Function CPU limits

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Learn how Edge Functions manage CPU resources and what happens when limits are reached.

How isolates work

An isolate is like a worker that can handle multiple requests for a function. It works until a time limit of 400 seconds is reached. Edge Functions use isolates with soft and hard CPU limits.

Soft limit

When the isolate hits the soft limit, it retires. This means:

• It won't take on any new requests
• It will finish processing requests it's already working on
• It keeps going until it hits the hard limit for CPU time or reaches the 400-second time limit, whichever comes first

Hard limit

If there are new requests after the soft limit is reached:

• A new isolate is created to handle them
• The original isolate continues until it hits the hard limit or the time limit
• This ensures existing requests are completed while new ones are managed by a fresh isolate

Current limits

• Wall clock time limit: 400 seconds total duration
• CPU execution time: 200 milliseconds of active computing

What happens when limits are exceeded

When your function exceeds CPU limits, you may see:

• 546 error responses
• Function termination with CPUTime shutdown reason
• Degraded performance as new isolates spin up

Optimizing CPU usage

Profile your code

Identify CPU-intensive sections in your function:

• Complex calculations
• Data processing loops
• Encryption operations

Optimize algorithms

• Use more efficient data structures
• Cache computed results
• Reduce algorithmic complexity

Offload heavy work

• Move intensive processing to background jobs
• Use external services for heavy computations
• Break large tasks into smaller functions

Additional resources

• Monitoring resource usage
• Edge Function shutdown reasons explained
• Edge Function limits