• .Net Core
• 24
• September-28-2025
• by Ihsan Ullah

Serverless APIs: A Guide to Building and Deploying

1. What are Serverless APIs?
Serverless APIs run on cloud-managed infrastructure where developers focus only on the API logic. The cloud provider (AWS Lambda, Azure Functions, Google Cloud Functions) handles provisioning, scaling, and availability. You pay only for execution time, not for idle servers.

2. Key Characteristics

• Event-driven: APIs trigger functions on HTTP requests, database updates, or queue messages.

• Automatic scaling: Functions scale up/down based on traffic without manual intervention.

• Stateless execution: Each function call is isolated; persistent data must be stored in external services (databases, storage).

• Pay-per-use: Billing is tied to number of requests and compute time.

3. Benefits

• Lower cost for low or unpredictable traffic.

• Faster development since no server management.

• Built-in resilience through distributed infrastructure.

• Rapid scaling during traffic spikes.

4. Challenges

• Cold starts: Delay on first request when function container is “warmed up.”

• State management: Requires external databases or caches (DynamoDB, Redis).

• Limited execution time/memory: Hard for long-running or heavy workloads.

• Vendor lock-in: APIs tied to provider-specific features.

• Monitoring and debugging: Distributed logs across ephemeral instances are harder to trace.

5. Building Process

1. Design API endpoints (REST or GraphQL).

2. Define function handlers for each route (login, getUser, createOrder).

3. Connect to cloud-managed API gateway that routes HTTP requests to functions.

4. Integrate storage/services (databases, queues, auth).

5. Configure IAM roles/permissions for secure access.

6. Deploy functions via CI/CD pipeline to the cloud.

6. Deployment Flow

• Local development: Test functions with mock events.

• Packaging: Functions and configuration are bundled.

• Infrastructure as Code (IaC): Tools like AWS SAM, Serverless Framework, or Terraform define APIs, functions, and resources.

• Deployment: Pushes to cloud provider. The gateway exposes public API endpoints.

• Monitoring: Logs and metrics are collected via cloud-native tools (CloudWatch, Application Insights).

7. Best Practices

• Keep functions small and single-purpose.

• Use API Gateway caching for repeated requests.

• Secure with authentication (OAuth2, JWT).

• Apply rate limiting and throttling.

• Structure logging and add distributed tracing.

• Plan fallback strategies for provider outages.

8. Typical Use Cases

• Mobile/web app backends.

• E-commerce order APIs.

• Chatbots and microservices.

• IoT device data ingestion.

• Event-driven workflows (file upload → trigger resize function).