API Design and Integration: The Practical Handbook

From your first endpoint to production-grade integrations, with examples in ASP.NET Core.

Welcome. This page is the starting point for a 12-chapter series on designing, building, and integrating APIs. Think of it as a book that you read one chapter at a time, right here on pronabroy.com.

Most API advice is scattered across blog posts, talks, and team wikis, and it rarely adds up to a clear picture. This handbook puts the topics in an order that makes sense. You start with what REST and HTTP actually mean. Then you design a solid contract, secure and harden it, and finish by running integrations in production. Each chapter builds on the one before it.

The code samples use ASP.NET Core and C#, but the ideas are language-agnostic. Where a topic is defined by a real standard, such as HTTP semantics in RFC 9110 or Problem Details in RFC 9457, the chapter links to the specification so you can go straight to the source.

Who This Handbook Is For

• Backend engineers (junior to mid-level) who want a structured, complete understanding of API design instead of a collection of tips.
• Senior engineers and tech leads who want a shared reference for API standards and code reviews.
• .NET and C# developers who want to see each concept implemented with current ASP.NET Core practices.
• Engineers on other stacks (Node.js, Java, Go, Python). The principles carry over, and the C# is easy to follow.
• Engineering managers and recruiters who want to see how a senior engineer thinks about API quality, trade-offs, and production readiness.

Prerequisites

You’ll get the most out of the series if you have:

• Comfort with at least one backend language (C# helps for the code samples).
• A basic idea of HTTP: what a request, a response, and a header are.
• Familiarity with JSON.
• For the hands-on parts: the current LTS release of the .NET SDK, an editor or IDE (Visual Studio, VS Code, or Rider), and an HTTP client such as curl, Postman, Bruno, or .http files.
• Optional: Docker, for running local dependencies like a database, an identity provider, or an observability stack.

What You’ll Build: ShipCart

Instead of isolated snippets, the chapters grow one fictional system called ShipCart. It has three parts:

• An e-commerce storefront API with products, carts, and orders.
• A logistics partner integration with shipments and tracking events from carriers.
• A SaaS layer with multi-tenant merchants, API keys, and usage plans.

Using one domain throughout means you see each new idea land in a codebase that keeps growing. Pagination arrives when the order list gets long. Idempotency arrives when a retried checkout must not create two orders. Webhooks arrive when merchants want to hear about shipment updates without polling.

How to Read This Series

The chapters are designed to be read in order. Part I gives you the vocabulary and mental model that the later parts rely on. If you already know a topic well, skim that chapter’s key takeaways and move on.

Every chapter follows the same pattern: a goal, the concepts, working code, a hands-on exercise, and key takeaways. Doing the exercises is the fastest way to make the ideas stick.

Prefer reading without distractions? Open the series in the built-in reader. It runs right here on the site, with a slide-out table of contents, next and previous buttons, and light, sepia, and dark themes. It also remembers where you stopped.

Table of Contents

Publishing Schedule

A new chapter is published every week, on the same day, until all 12 chapters are live. As each one goes up, its entry in the table of contents above becomes a link. Bookmark this page as your map of the series.

About the Author

Pronab Roy is a senior backend engineer who designs and builds APIs and the integrations between them. His day-to-day work covers the topics in this handbook: shaping clear contracts, securing endpoints, connecting to third-party services, and keeping systems observable and reliable in production. He writes for engineers who want practical, standards-based guidance they can apply on their next pull request.

Follow Along

Want to know when the next chapter is out? Follow Pronab Roy on LinkedIn for each new chapter, plus short notes on API design along the way.

Ready to begin? Start with Chapter 1: What Makes a Good API? REST and HTTP Fundamentals →