Grokking Modern API Design Interview

It is a course on designing APIs under interview conditions. It teaches a six-step method that takes a one-line question through to a complete contract: the consumers and the jobs they need to finish, the resources, the operations, one operation designed field by field, the hard parts such as idempotency and rate limiting, and the trade-offs you chose. It covers REST first, then gRPC and GraphQL, real time delivery, APIs for AI products, and the product architecture round, across 8 chapters and 68 lessons with 243 diagrams.

Software engineers preparing for an API design round, a system design interview, or a product architecture interview, from mid level upward. It also suits engineers who build APIs every day but have never had to justify one out loud in 45 minutes, and anyone whose designs work in production yet lose points in interviews for missing versioning, idempotency, or an error contract a caller can act on.

A system design interview asks how a product scales, so the answer is services, databases, caches, queues, and the trade-offs between them. An API design interview asks what the contract is, so the answer is operations, resource shapes, field types, status codes, error bodies, and the promises you make to callers about compatibility. The two rounds overlap, and most system design interviews pause on a contract at some point, but a scaling answer does not earn credit in a round that is grading the contract.

No. The course is language independent, because an API contract is not written in an application language. The examples are HTTP requests and responses, JSON bodies, Protobuf service definitions, and GraphQL schemas, which are the same artifacts you would put on a whiteboard or in a shared document during the interview.

There are 15 complete designs. The five capstones are a URL shortener, the Twitter API, a live notification API, a payment API, and an LLM inference API. The other ten are a chat API, a booking API, a feature flag API, a checkout API, a calendar API, a collaborative document API, the API behind a news feed screen, the API behind a messaging app, a ride sharing API, and a file storage API. A separate lesson hands you a deliberately broken API and asks you to critique it, which is a question type interviewers use more often than candidates expect.

Identify the consumers and the jobs they need to finish, model the resources, list the operations, design one operation in complete detail, address the hard parts, and state the trade-offs you took along with the options you rejected. The course budgets those steps at 5, 5, 10, 10, 10, and 5 minutes for a 45-minute round, and shows how to halve every step except the fourth when you only get 30 minutes, because one fully designed operation is the evidence the round exists to collect.

Yes. A full chapter designs a gRPC service contract and a GraphQL schema, then compares all three so you can name the trigger that makes one of them the right answer rather than picking by preference. The same chapter covers real time delivery with WebSockets, server sent events, and long polling, webhooks as the API that calls you back, asynchronous APIs for long running work, and large uploads and downloads.

Because those contracts are genuinely different, and interviewers have started asking about them. A response that streams as it is generated needs event types and a stated reason for stopping. An agent needs operations a model can choose between without guessing. Compute that costs real money per call needs metering, billing, and rate limits designed into the contract rather than added afterwards. The chapter covers each of those and ends by designing a complete LLM inference API.

It is an interview where the API has to serve a real product screen, so you are graded on the data model and the client call flow as well as the contract itself. The chapter covers turning a feature into a data model, designing for one screen without forcing it into too many round trips, and handling offline edits that conflict, then works through the API behind a news feed and the API behind a messaging app.

Text-based, with 243 diagrams and contracts you can read in place. That suits API design better than video, because most of your time goes on comparing a request against the response it produces, and checking one field against the rule that governs it, and moving back and forth between the two is far easier on a page than in a timeline.

Yes. Design Gurus issues a certificate once you have completed the course, and you can share the link directly or add it to your LinkedIn profile.