Grokking Modern API Design Interview: What Is Inside the Course

Grokking Modern API Design Interview is a text based course on the API design round. It has 8 chapters, 76 lessons, 243 diagrams, and 15 complete designs worked from a one line brief to a finished contract. It costs $123 for lifetime access.

This page is written by us, so treat it as a description rather than an independent review. It says what is in the course, who it suits, and what it does not include, so you can decide before paying.

The short version

What the eight chapters cover

1. The API Design Interview. What the round is, how it differs from system design, what interviewers grade, and the six step method used through the rest of the course. Ends with a URL shortener API as a first capstone.

2. Designing a REST API. Resource modelling, HTTP method semantics, URL design, request and response shapes, status codes and error design, pagination, filtering, and bulk operations. The capstone is the Twitter API.

3. When REST Is Not Enough. gRPC contract design, GraphQL schema design, and the rules for choosing between the three. Then real time delivery with WebSockets and server sent events, webhooks, async work, and large uploads. The capstone is a live notification API.

4. The Hard Parts. Idempotency keys, rate limiting in the contract, authentication and authorisation, multi tenancy, versioning and backward compatibility, concurrency and conditional requests, caching, and the reliability contract. The capstone is a payment API.

5. APIs for AI Products. Streaming responses from language models, designing APIs that agents call, usage metering and billing, and rate limiting expensive compute. The capstone is an inference API.

6. More Interview Questions. Six full questions worked end to end: chat, booking, feature flags, checkout, calendar, and a collaborative document API.

7. The Product Architecture Round. Going from a feature description to a data model, then designing for one screen. Offline sync and conflict resolution follow, plus two worked questions on a news feed and a messaging app.

8. Full Answers and Quick Review. A ten minute answer template, then three more worked questions including a ride sharing API and a file storage API. Then a critique exercise, rapid fire questions, and decision cheat sheets.

Who it is for

A backend or platform engineer with an interview booked. This is the main audience. If a company has told you there is an API design round, this covers it directly.

Anyone interviewing at an API first company. Stripe, Twilio, Shopify, Plaid, and Square run this round because the API is the product. So do many smaller companies selling developer tools.

Engineers who design APIs but never learned it formally. Most people pick this up by copying whatever the last team did. The chapters on idempotency, versioning, and error design are the parts that usually never got taught.

Who it is not for

People who want video. Every lesson is text and diagrams. That is faster to skim and search, but if you learn by watching, this is the wrong format.

People who need coding practice. There is no code editor and no test runner. The course designs contracts. For implementation practice, a coding course is the better spend.

Complete beginners. The lessons assume you know what HTTP is and have called an API before. They do not assume you have designed one.

Anyone whose interview is pure system design. If the round is "design Instagram" with capacity estimates and sharding, Grokking the System Design Interview is the better fit. Some overlap exists, but the emphasis is different.

What it does not include yet

The course does not have quizzes, flashcards, or graded assessments. Other courses in the catalogue do, and this one is newer. If you rely on self testing to know whether something stuck, that gap matters. The honest answer is that you would supply it yourself for now.

There is also no video, no mock interview built in, and no code execution. Mock interviews are sold separately.

How it compares to the other courses

The API design course assumes the fundamentals rather than teaching them. If terms like idempotent, cursor, and backward compatible are new, start with Fundamentals and come back.

Free ways to try it first

Several lessons are readable without buying anything. Three worth starting with:

• A framework for API design answers, which is the six step method the whole course runs on.
• Idempotency keys, the single most asked follow up question in this round.
• REST vs gRPC vs GraphQL, the protocol choice question.

There is also a free open source guide on GitHub, Grokking System Design, which covers the wider system design ground. It is not the API course, and it is not a copy of it, but it is a genuine free starting point.

If you would rather read something short first, API design interview questions works ten of the same problems in outline.

Frequently asked questions

Is Grokking Modern API Design Interview worth it?

If you have an API design round booked, it is the only course in the catalogue built for that round. Lifetime access costs $123. If your interview is general system design, or you mostly need coding practice, your money goes further elsewhere.

What is the difference between this and Grokking the System Design Interview?

This one designs contracts: endpoints, payloads, status codes, idempotency, versioning. The system design course designs systems: storage, caching, sharding, replication, and capacity. Some companies run both rounds, and the two courses do not repeat each other.

Does the course have video?

No. Every lesson is text with diagrams. That makes it fast to search and skim, and a poor fit if you prefer watching.

Does it include quizzes or flashcards?

Not yet. Other Grokking courses have them and this one is newer, so plan to self test another way for now.

Is there a free version?

Several lessons are readable for free, including the framework lesson and the idempotency lesson linked above. The open source Grokking System Design repo on GitHub is free and covers the broader system design ground.

How long does it take to finish?

76 lessons at roughly ten minutes each is about twelve hours of reading. Most people work through the chapter that matches their interview first, then the capstones, rather than reading front to back.

Does it cover AI and LLM APIs?

Yes, chapter 5 is about that: streaming responses, APIs that agents call, usage metering and billing, and rate limiting expensive compute. That chapter is the main thing separating this from older API design material.

Related Reading

• API design interview questions
• API interview questions
• How to design a RESTful API
• Types of system design interviews