Technical interviews at top companies test a range of skills beyond just LeetCode. Backend roles require deep understanding of systems, databases, and concurrency. Frontend roles test JavaScript internals and performance. Full-stack roles test both. This guide covers the core areas every engineer should master before their next technical round.
Core data structures to master
- Arrays and strings — sliding window, two pointers, prefix sums
- Hash maps and sets — frequency counting, fast lookups, deduplication
- Linked lists — reversal, cycle detection, merge operations
- Trees and graphs — BFS, DFS, topological sort, Dijkstra
- Heaps and priority queues — top-K problems, merge K lists
- Stacks and queues — monotonic stacks, sliding window maximum
Backend-specific topics
- How the event loop works in Node.js (libuv, async I/O, microtask queue)
- JWT authentication — structure, signing, refresh token rotation
- Database indexing — B-trees, composite indexes, query planning
- The N+1 problem — eager loading, DataLoader, join queries
- Caching strategies — cache-aside, write-through, TTL, invalidation
- REST vs GraphQL trade-offs — when to choose which
How to approach problems in the interview
- Clarify before you code — ask about constraints, edge cases, input size
- Think out loud — interviewers want to follow your reasoning
- Start with a brute force — then optimise, explaining each improvement
- Test your solution — trace through an example by hand before declaring done
- Know your complexity — state time and space complexity without being asked
Simulate real technical interviews
MockFlux lets you practice technical interview questions across different roles, difficulties, and question types. After each session, you receive structured AI feedback on your answer quality, the concepts you covered, the key terms you missed, and a sample answer to compare against.