What are the main limits of AWS Lambda, such as timeout and memory?
A Lambda function can run for at most 15 minutes per invocation and be given 128 MB to 10,240 MB of memory. CPU power scales with the memory you choose. It also has limits on package size and account concurrency.
Explain it simply
Lambda is a short-shift worker, not a permanent employee. It is called, does a job, and must finish within the shift. If your job runs for hours, Lambda is the wrong tool.
Example
Max duration per invocation : 15 minutes (900 seconds)
Memory : 128 MB up to 10,240 MB
CPU : no separate setting; more memory gives more CPU
Concurrency : default account limit per Region, can be raised
Ephemeral /tmp storage : 512 MB by default, configurable higherYou set timeout and memory per function. Increasing memory often makes a CPU-bound function finish faster, so the total cost can stay similar or even drop, because you pay for memory multiplied by duration.
Because there is a 15-minute cap, long jobs such as video transcoding or big data loads go to ECS/Fargate, AWS Batch or Step Functions that splits the work into smaller Lambda calls. Never rely on /tmp for permanent data; the environment can disappear at any time.
What to say in the interview
"Lambda is capped at 15 minutes per run, with memory from 128 MB to 10 GB and CPU tied to memory. If a job exceeds that I move it to Fargate or Batch, or split it with Step Functions. I tune memory by testing, since more memory can mean a shorter, cheaper run."
Common mistakes
- Believing Lambda can run a long-lived server process.