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A practical guide to coding interviews — from data structures to system design to behavioral questions.
Most tech interviews have three types of rounds:
| Round | What they test | Duration | | ----------------- | ------------------------------------------------- | --------- | | Coding | Problem-solving with data structures & algorithms | 45-60 min | | System Design | Architecture and scalability thinking | 45-60 min | | Behavioral | Communication, teamwork, conflict resolution | 30-45 min |
Entry-level roles focus heavily on coding. Senior roles add system design. All levels include behavioral questions.
The key insight: interviews test your thought process, not just your answer. Talking through your approach matters as much as getting it right.
Knowing the format helps you prepare strategically.
You don't need to know every data structure — but you need these cold:
Arrays & Strings:
Hash Maps — O(1) lookup, the most useful interview tool:
Stacks & Queues:
Master arrays, hash maps, stacks, and trees — they cover 80% of coding questions.
Use this framework for every coding problem:
Example walkthrough:
"Given a string, find the length of the longest substring without repeating characters."
Always plan before coding. Interviewers value structured thinking.
System design questions test your ability to think at scale:
"Design a URL shortener like bit.ly"
Framework:
Key concepts to know:
System design is about trade-offs, not perfect answers.
Behavioral questions assess soft skills. Use the STAR method:
Common questions and how to prepare:
| Question | What they're testing | | ---------------------------------------------------- | ----------------------------- | | "Tell me about a time you disagreed with a teammate" | Conflict resolution | | "Describe a project you're proud of" | Passion, technical depth | | "Tell me about a time you failed" | Self-awareness, growth | | "How do you handle tight deadlines?" | Prioritization, communication |
Pro tip: Prepare 5-6 stories that cover different themes. Each story can answer multiple questions by emphasizing different aspects.
Have your stories ready. Practice telling them out loud.
Week 1-2: Foundations
Week 3-4: Pattern Recognition
Week 5-6: Mock Interviews
Daily habits:
Consistency beats intensity. Build a daily practice habit.
Before the interview:
During the interview:
Questions to ask your interviewer:
Preparation breeds confidence. You've got this.
What's next? Learn How to Read Documentation Effectively — a skill that separates self-sufficient engineers from those who are always asking for help.
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