Grokking Modern API Design Interview

What the course covers

The course, now titled Grokking Modern API Design Interview: REST, gRPC and AI, is organised into eight chapters (as listed on the course page in September 2026):

1. The API design interview (9 lessons): a framework for the round, how to gather requirements and what interviewers grade.
2. Designing a REST API (14 lessons): resources, HTTP methods, URL design, status codes, pagination and filtering.
3. When REST is not enough (10 lessons): gRPC, GraphQL, WebSockets, webhooks and asynchronous APIs, and how to choose between them.
4. The hard parts: failures, security and change (12 lessons): idempotency, rate limiting, authentication and authorisation, versioning and caching.
5. APIs for AI products (7 lessons): streaming LLM responses, APIs for agents, usage metering and billing.
6. More interview questions (8 lessons): chat, booking, feature flags, checkout, calendar and collaborative documents.
7. The product architecture round (7 lessons): data models, designing the API behind a single screen, and offline sync.
8. Full answers and quick review (9 lessons): ten minute answers, rapid fire questions and decision guides.

Across the course there are 15 complete API designs, including a URL shortener, a Twitter style API, a payment API, an LLM inference service, a news feed, a messaging app, ride sharing and file storage, plus an API critique exercise.

Numbers at a glance

As shown on the course page in September 2026: 76 lessons, about 20 hours of material, an intermediate level, a 4.7 out of 5 rating from 389 ratings and 3,119 learners. A certificate is issued on completion. The course page listed it as a one time payment of $123 with lifetime access at that time; check the page for the current price and any bundle options.

Why API design deserves its own preparation

APIs are the hardest part of a system to change, because the cost of a breaking change lands on clients you do not control. Interviewers know this, which is why a candidate who raises versioning strategy, idempotent writes and pagination without being prompted stands out. Many engineers prepare for general system design and are then surprised by a round that focuses entirely on the interface. This course targets that round directly.

Who it suits

• Backend and platform engineers with a year or more of experience who have built APIs but never had to defend design choices.
• Engineers preparing for rounds labelled API design, product architecture or product design.
• Full stack developers who want to move from "it works" endpoints to APIs other teams enjoy using.

You should already be comfortable with HTTP basics and have built at least one API in any language.

How to get the most out of it

• Work chapter 4 twice. Idempotency, rate limiting, auth and versioning are where answers are won or lost.
• Design before reading. For each of the 15 case studies, sketch your own endpoints, request and response shapes and error cases first, then compare.
• Redesign an API you built. Take a real project and rewrite its endpoints against what you learned. The specific mistakes you find are what you will remember.
• Practise out loud. Use the ten minute answers in chapter 8 as a template and time yourself explaining a design.
• Use the AI chapter if relevant. Streaming and metering questions are increasingly common for teams building LLM products.

Common questions

How long does it take? About 20 hours of material. Most learners finish in two to four weeks at a few hours a week.

Is it only about REST? No. REST is the core, but gRPC, GraphQL, WebSockets, webhooks and async APIs each get proper treatment.

Pair it with: the relational database design course in this library, since a strong API design depends on a sound data model underneath.

Best for: backend engineers who want a structured, practical way to design and explain APIs under interview conditions.