Subjects Questions Quizzes Pricing
System Design · Algorithms · Engineering

Master Engineering Concepts

Structured subjects, practice questions, and timed quizzes — everything you need to level up your system design skills.

12 pieces of content · Free subjects included

Top Subjects

Most popular content to start with

View all →
Pro Databases
Intermediate

Database Indexing

Learn how B-tree and hash indexes work internally, how the query planner uses them, when to create composite and covering indexes, and how to diagnose slow queries using EXPLAIN ANALYZE.

16 min
Free System Design
Beginner

System Design Basics

Learn the fundamental principles behind building large-scale, reliable systems: scalability, availability, latency, and the key trade-offs that drive real-world architecture decisions.

12 min
Pro System Design
Advanced

Consistent Hashing

Understand the hash ring, virtual nodes, and why consistent hashing is the foundation of distributed caches (Redis Cluster, Memcached), distributed databases (Cassandra, DynamoDB), and CDN request routing.

18 min
Free System Design
Beginner

Load Balancing

Understand how load balancers work, the algorithms they use (round-robin, least-connections, IP hash), Layer 4 vs Layer 7 differences, and how to design systems that stay healthy when servers fail.

10 min
Pro System Design
Intermediate

The CAP Theorem

Understand why distributed systems can only guarantee two of Consistency, Availability, and Partition Tolerance — and how real-world databases (Cassandra, Zookeeper, DynamoDB, Postgres) navigate this fundamental constraint.

14 min
Free System Design
Intermediate

Concurrency vs Parallelism

Untangle four words engineers constantly confuse: concurrency, parallelism, threads, and processes. Learn what runs truly simultaneously versus what merely interleaves, why Python's async model is single-threaded, and how getting this wrong causes real production bugs like sharing one database session across coroutines.

14 min

Practice Questions

Sharpen your skills with real interview questions

View all →

Structured Subjects

Deep-dive lessons on system design, databases, algorithms, and networking — with a clear learning path.

Practice Questions

Hundreds of questions with step-by-step solutions. Reveal answers when you're ready, at your own pace.

Timed Quizzes

Test yourself under real conditions. Complete a quiz to unlock the subject rating and track your progress.