Serverless cold start refers to the process of initializing the runtime environment, loading dependency packages and code when a function is called for the first time or after a long period of inactivity, which results in additional latency. Cold start time typically ranges from a few hundred milliseconds to a few seconds.
Factors affecting cold start:
- Runtime language: Node.js and Python are faster, Java and .NET are slower
- Code package size: More dependencies mean longer load times
- Memory configuration: Larger memory allocation can speed up startup
- VPC configuration: Configuring VPC increases network initialization time
- Warm-up strategy: Periodically triggering functions to keep instances active
Optimization strategies:
- Code optimization: Streamline dependencies, use lightweight frameworks
- Warm-up mechanism: Use scheduled triggers to keep functions warm
- Concurrency configuration: Set appropriate reserved concurrency instances
- Runtime selection: Choose languages with fast startup times
- Architecture design: Place critical paths in resident services
Candidates should be able to explain how to assess the impact of cold starts on business and what optimization measures were taken, based on actual project experience.