Serverless Functions Guide for Modern Web Apps

Serverless functions are small pieces of backend code that run on-demand without managing servers. When a request arrives, the cloud provider spins up an execution environment, runs your function, and shuts it down when done. You pay only for the compute time you use. Platforms like Vercel, AWS Lambda, Cloudflare Workers, and Netlify Functions all offer serverless capabilities. For startups, serverless eliminates the operational overhead of managing server infrastructure.

Serverless functions are ideal for API endpoints, webhook handlers, scheduled tasks, and event processing. They excel when traffic is unpredictable because they scale automatically from zero to thousands of concurrent executions. However, serverless has limitations. Cold starts add latency to the first request after a period of inactivity. Long-running processes that exceed timeout limits need a different approach. Persistent WebSocket connections are difficult to implement in most serverless environments.

Vercel provides the simplest serverless experience for Next.js developers. API routes in your `pages/api` or `app/api` directory are automatically deployed as serverless functions. Each function has a maximum execution time of 10 seconds on the free tier and up to 300 seconds on paid plans. Vercel functions run on AWS Lambda under the hood but abstract away all configuration. Edge Functions run on Cloudflare's network for even faster response times at the cost of a more limited runtime environment.

AWS Lambda is the original and most mature serverless platform. It supports many languages including Node.js, Python, Java, Go, and .NET. Lambda functions can be triggered by HTTP requests through API Gateway, messages from SQS queues, file uploads to S3, and many other AWS events. The maximum execution time is 15 minutes. Lambda provides fine-grained control over memory allocation, VPC networking, and concurrency limits. The tradeoff is significantly more configuration compared to simpler platforms.

Cloudflare Workers run at the edge in over 300 cities worldwide, providing the lowest latency of any serverless platform. They use the V8 JavaScript engine directly rather than Node.js, which means some Node.js APIs are not available. Workers have a 10 millisecond CPU time limit on the free tier and 30 seconds on paid plans. They work well with Cloudflare's ecosystem including KV storage, D1 database, and R2 object storage. For latency-sensitive applications, Workers are hard to beat.

Keep your serverless functions focused on a single responsibility. Minimize cold start times by reducing your bundle size and avoiding heavy dependencies. Use connection pooling for database connections since serverless functions may create many short-lived connections. Implement proper error handling and logging since debugging serverless functions is harder than traditional servers. Cache responses when possible to reduce function invocations and improve response times.

Designing a serverless architecture requires different thinking than traditional server-based applications. Database connection management, cold start optimization, and function composition patterns all need careful consideration. AI-generated code often does not account for serverless constraints like execution timeouts and stateless execution. SpringCode architects serverless backends that handle these constraints properly, giving you scalable infrastructure without the operational burden.