Optimizing cold starts is crucial for ensuring the responsiveness of serverless-based applications. A cold start occurs when the execution environment of a function needs to be initialized from scratch, which can cause delays during the first few invocations. Here are five key actions to minimize these delays and improve the performance of your applications.
A real-life metaphor: the coffee and our file processing API
At HK-TECH, we developed a file processing API for a client. Although the API worked well on the surface, it suffered from instability, especially after periods of inactivity. It was like arriving at the office after a long weekend and having to wait for the cold coffee machine to warm up before enjoying a cup. This wait was frustrating for users, particularly when they needed an immediate response.
The cold start was like that cold coffee machine. Each time the API was called after a long idle period, the initial startup delay wasted precious time. We had to reassess our approach and optimize our serverless architecture so that the API would be ready as quickly as an espresso served when the machine is already hot.
5 Key Tips to Reduce Cold Start:
1. Import only necessary functions when calling a library
It is common to import entire libraries, but this can increase the function’s loading time. Importing only the modules or functions needed helps reduce the code size, which can speed up the startup time.
Tip: Use specific imports like from library import needed_function instead of import library.
2. Leverage layers
Layers help separate code and dependencies from your functions, which can reduce deployment package size and simplify maintenance. Using layers for shared libraries can lighten the function’s loading time.
Tip: Place common dependencies in a layer and use it across multiple functions to increase efficiency.
3. Don’t skimp on resources, especially memory
Allocating more memory to your functions can proportionally increase the processing power. A function with more memory often starts faster, as the environment is optimized for better performance.
Tip: Test different memory configurations to find the best balance between performance and cost.
4. Eliminate unused code
Unused code in your functions can clutter your codebase and increase the function’s loading time. Regularly cleaning up your code can optimize the loading phase.
Tip: Perform regular code reviews to remove anything outdated or unnecessary.
5. Avoid large Lambda functions that do too much; use smaller functions instead
A Lambda function that handles too many responsibilities can become bulky, which increases the startup time. By creating multiple smaller functions dedicated to specific tasks, you can achieve faster startups and easier code maintenance.
Tip: Apply the Single Responsibility Principle to segment your functions effectively.
Conclusion
Reducing cold starts is a challenge, but by following these best practices, you can significantly improve the performance and responsiveness of your serverless applications.
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I’m Hervé-Gaël KOUAMO, Founder and CTO at HK-TECH, a French tech company specializing in designing, building, and optimizing applications. We also assist businesses throughout their cloud migration journey, ensuring seamless transitions and maximizing their digital potential. You can follow me on LinkedIn (I post mostly in French there): https://www.linkedin.com/in/herv%C3%A9-ga%C3%ABl-kouamo-157633197/
