apfyre

What's inside

Over 3,500 questions across 70+ topics, covering the software engineering that interviews and day-to-day work rely on. Each one is written to be answered in a spare five minutes rather than a study session.

• Multiple choiceThe fundamentals, and why the other three answers are wrong.
• Fill the missing lineA snippet with a hole in it, which you can't bluff.
• Order the linesReassemble a function from shuffled lines.
• Spot the bugReal code with one thing wrong in it. Find it.

Languages

Bash, C, C++, C# & .NET, Go, Java & JVM, JavaScript, Kotlin, Python, Ruby, Rust, Scala, Swift, TypeScript

Frameworks

Angular, ASP.NET Core, Django, EF Core, FastAPI, Hibernate & JPA, NestJS, Node.js, React, Spring Boot, Vue

Infrastructure and cloud

AWS, Azure, CI/CD, Cloud Computing, Docker, GCP, Git, Kubernetes, Observability & SRE, Terraform

Data and messaging

GraphQL, gRPC, Kafka, Message Queues, MySQL, NoSQL Databases, PostgreSQL, Redis, REST API Design, SQL, SQL Queries

Runtimes and the web

Browser & DOM, CLR & GC, CPython Runtime, Go Runtime, HTTP & the Web, JVM & GC, Networking, V8 & Event Loop

Fundamentals

Algorithm Patterns, Complexity, Concurrency, Data Structures, Design Patterns, Distributed Systems, General CS, Machine Learning & AI, OOP Concepts, Security, SOLID Principles, Software Process, System Design, Testing & QA

Code-reading drills

Coding Challenges, Predict the Output, Spot the Bug, Spot the Inefficiency, Spot the Vulnerability, What Breaks This?

Dig deeper with AI. Every question you review carries a link that opens your chosen assistant — Claude, ChatGPT, Copilot, Gemini or Grok — with the question, your answer and the explanation already written out. You ask the follow-up; you don't retype the context.

Free in every topic. Questions come in three levels. Foundation is free across all of them, so you can try the whole breadth of the app without paying; Pro adds Intermediate and Advanced and removes the advert.