Cramming at
1 AM again?

You're not an imposter. You just haven't reviewed.

Sweat now, breeze the on-site.

Nobody needs to know you forgot quicksort.

Valid Palindrome

easy · neetcode150

Today's tour · one of each

Idempotency Keys

Memcached vs Redis

Tell me about a time you gave someone difficult feedback. How did they receive it?

Cost of one wait() call in epoll (edge-triggered, ready list) when there are n watched file descriptors and k are ready?

Wrong base case

Long-running operations

Multi-tenant isolation

Object-Oriented Design

Elevator System

Suffix structures

Database Design

Audit / Event Log

Database Concept

Replication Patterns

Solve

Read a problem, formulate the approach, reveal the canonical solution.

Pattern Triage

See a problem, name the pattern. Multiple choice — recognition only.

Big O Quiz

Complexity of operations, data structures, and standard algorithms — no code.

System Design Components

Pick the building blocks for a classic system-design prompt.

Behavioral

STAR-style prompts with rubrics. The 30-50% you can't skip.

Write

Type the actual code in Java or Python; compare to the canonical when you're done.

Techniques Quiz

Scenario → which production idiom (backoff, idempotency, bloom, leases)?

Systems & Concurrency

Concurrency, distributed, database, networking — scenario quiz across all four.

Code Review

Read 30 lines, find the race / N+1 / SQL injection / off-by-one. Pick from 4.

Debugging

Function + failing test (input, expected, actual). Find the bug.

API Design

Given a use case, pick the best endpoint — method, path, body, status codes.

SQL Drills

Schema + question, pick the correct query. JOINs, window functions, NULL traps.

Security

OWASP, auth, JWT, CSRF, secrets — the things every senior is expected to know.

Object-Oriented Design

Parking lot. Elevator. Chess. Pick the prompt, design the classes, compare.

Algorithms

Dijkstra, MST, KMP, Fenwick — beyond BFS/DFS. Pick the right tool.

Database Design

Schema design prompts — chat, e-commerce, multi-tenant. Tables, indexes, sharding.

Concepts

Recall-style: "When do you use X?", "Explain Y." Think first, then reveal. No multiple choice.

Evolving Scenarios

Same system, scale escalates. Each stage adds a constraint — pick the next move. Your stack builds up.

System Design Deep Dive

Same system, facet by facet — capacity, architecture, API, data model. Think before each reveal. Grokking-style.

Tradeoff Cards

Pick A or B for the scenario, learn the canonical answer.

Complexity Drill

Read a snippet, name its time and space.

Flashcards

Pattern definitions, when to use, self-rated.

Or simulate the real thing

Mock interview

Timed mixed-mode session — pick a preset and run it. End-of-session report shows what to drill next.

Follow a curated path

Study tracks

Junior / Mid / Senior — curated curriculum of patterns, problems, SD, techniques, and behavioral, sized for the level.

Or read the reference

Library

Encyclopedia of every concept — patterns, system design, tradeoffs, techniques, SQL, security, OOP and database design, with cross-links. Read up before drilling.