Tech Interview Prep Cheatsheet

💼 Interviews

Tech Interview Prep

Behavioural questions, DSA patterns, system design, and negotiation — complete interview cheatsheet.

📖 6 sections

⏰ 18 min read

✅ Quizzes included

01Behavioural Questions (STAR)▼

INTERVIEWSTAR method

STAR = Situation, Task, Action, Result

Q: "Tell me about a time you solved a difficult problem."
S: Situation - "Our API was returning errors for 20% of users."
T: Task      - "I was responsible for identifying the root cause."
A: Action    - "I added logging, traced errors to a race condition,
               then implemented a mutex lock."
R: Result    - "Error rate dropped to <0.1% within 2 hours."

Tell me about yourself

1. Current role (30s), 2. Relevant experience (30s), 3. Why this role (30s). Keep under 90 seconds.

Why this company?

Research the company! Mention: specific product you use, their tech stack, mission alignment, recent news.

Greatest weakness

Pick REAL weakness + show improvement: "I used to avoid asking for help. Now I set a 30-min timer before escalating."

Where do you see yourself?

Align with role growth. "I want to become a senior engineer and mentor juniors — this role gives that path."

02DSA Interview Patterns▼

Pattern	When to use	Key technique
Two Pointers	Sorted array, pair sum, palindrome	left/right pointer moving inward
Sliding Window	Subarray/substring, fixed or variable size	Expand right, shrink left
Fast & Slow Pointers	Cycle detection, middle of linked list	slow+=1, fast+=2
Binary Search	Sorted input, find target or boundary	lo/hi/mid, eliminate half each step
BFS	Shortest path, level order, graph	Queue, visited set
DFS	All paths, tree traversal, backtracking	Stack/recursion, visited
Dynamic Programming	Overlapping subproblems, optimal value	Memoize or tabulate
Monotonic Stack	Next greater/smaller, histogram	Maintain increasing/decreasing stack

💡

For any array problem: consider sorting first. For any string problem: consider a hashmap for frequency counting.

03System Design Framework▼

INTERVIEWSD interview steps

1. CLARIFY requirements (5 min)
   - Functional: what must it do?
   - Non-functional: scale, latency, availability?
   - Constraints: daily active users, data volume?

2. ESTIMATE scale
   - 1M DAU x 10 requests/day = 10M req/day = ~115 req/sec
   - Storage: 1M users x 1KB profile = 1GB

3. HIGH-LEVEL design
   Client -> Load Balancer -> App Servers -> Cache -> DB

4. DEEP DIVE
   - Database choice (SQL vs NoSQL, why?)
   - Caching strategy (Redis, what to cache?)
   - API design (REST endpoints)
   - Scaling bottlenecks

5. TRADE-OFFS
   - CAP theorem, consistency vs availability

SQL vs NoSQL

SQL: structured data, ACID, relations. NoSQL: flexible schema, horizontal scale, high write throughput.

Cache when

Frequently read, rarely written data. User sessions, hot content, computed results.

Message queue

Decouple services, handle spikes. Kafka=high throughput, RabbitMQ=routing.

04Coding Interview Tips▼

Read the problem twice

Identify: input/output types, edge cases, constraints. Ask clarifying questions BEFORE coding.

Talk while coding

Explain your thought process. Interviewers want to see HOW you think, not just the answer.

Start with brute force

State the O(n2) solution first. Then optimize. Shows you can reason through complexity.

Test your code

Trace through with example. Check edge cases: empty input, single element, negatives.

Big-O analysis

Always state time AND space complexity. Know how to derive it from loops and recursion.

Clean code

Meaningful variable names. Small functions. No magic numbers.

INTERVIEWProblem solving template

1. Read + Clarify (2 min)
2. Examples: draw/trace 2-3 examples
3. Brute force approach + complexity
4. Optimal approach + complexity
5. Code it up
6. Test: happy path, edge cases
7. Optimize if time allows

05Salary Negotiation▼

Never give first number

Say: "I'd like to understand the full comp package first." Or give a range based on research.

Research market rate

Glassdoor, Levels.fyi, LinkedIn Salary, Blind. Know your number before the call.

Negotiate everything

Base salary, equity, signing bonus, vacation days, remote work, title, review timeline.

Counter-offer script

"I'm very excited about this role. Based on my research and experience, I was expecting [X]. Is there flexibility?"

Competing offer

Best leverage. "I have an offer for [X] from [Company]. I prefer your role — can you match it?"

Get it in writing

Never accept verbally. Ask for the offer letter before giving notice.

💡

The hiring manager almost always expects you to negotiate. Not negotiating leaves money on the table. The worst they can say is no.

06Resume & LinkedIn▼

INTERVIEWResume bullet formula

STRONG: "Reduced API response time by 40% by implementing Redis caching,
         improving user retention by 12%."

WEAK: "Worked on backend improvements to make things faster."

Formula: [Action verb] + [what you did] + [measurable result]

Action verbs: Built, Designed, Optimized, Reduced, Increased,
              Led, Implemented, Automated, Refactored, Deployed

ATS optimization

Use keywords from the job description. Standard headings: Experience, Education, Skills, Projects.

Projects section

Include: what it does, tech stack, your specific role, results/metrics if any.

Headline = current role + 2-3 skills. Summary = 3 sentences. Add all skills section.

GitHub

Pin 4-6 best repos. Add README with screenshots, tech stack, and how to run.