What is a serverless backend?

A serverless backend is a cloud computing model where developers build and deploy applications without managing the underlying servers or infrastructure. Instead of provisioning and maintaining servers, the cloud provider (like AWS, Azure, or Google Cloud) automatically allocates resources to run code in response to events or requests. The term “serverless” can be misleading because servers are still involved, but their management is abstracted away. Developers focus solely on writing code for specific functions or services, which are executed in ephemeral, stateless environments. For example, a serverless function might process an image upload, handle an API request, or trigger a database update—all without the developer worrying about server uptime, scaling, or patches.

A key feature of serverless backends is event-driven execution. Functions are triggered by specific events, such as HTTP requests (via an API Gateway), changes in a database (like DynamoDB streams), or file uploads to cloud storage (e.g., AWS S3). When an event occurs, the cloud provider spins up a container to run the function, processes the task, and shuts down the container when idle. This on-demand model ensures you only pay for the compute time used during execution, not for idle resources. For instance, an e-commerce app might use a serverless function to send a confirmation email after a purchase. The function runs only when a checkout event occurs, scaling automatically during peak traffic without manual intervention.

While serverless backends simplify infrastructure management, they come with trade-offs. Cold starts—delays when a function initializes after being idle—can impact performance for latency-sensitive applications. Execution time limits (e.g., 15 minutes on AWS Lambda) make serverless unsuitable for long-running tasks like video encoding. Vendor lock-in is another concern, as functions often rely on proprietary cloud services (e.g., AWS Step Functions). However, serverless excels for use cases like REST APIs, real-time data processing (resizing images on upload), or scheduled tasks (daily report generation). Tools like the Serverless Framework or AWS SAM help automate deployment, and services like CloudFront or API Gateway handle routing. By offloading infrastructure concerns, developers can iterate faster, but they must design around statelessness, short-lived processes, and distributed system complexities.