How to Prepare for Coding Interviews

Coding interviews are their own skill. Strong engineers who don’t prepare routinely bomb them, and mediocre engineers who prepare well get offers. The good news: the skill is narrow, trainable, and the return on preparation is enormous — an offer from a top employer can change your income by six figures annually.

This guide is the efficient-prep version, not the 500-hour LeetCode version. Most candidates can get where they need to be with 40–100 focused hours, spread over 8–12 weeks.

1. Pick the target company level first

Prep depth varies with target. FAANG L4/L5 roles need systems design and algorithms under time pressure. Series-B startup might be a take-home and a real-world coding pairing. Know what you’re walking into before you spend a month on dynamic-programming drills you’ll never use.

2. Know the patterns, not the problems

There are about 15 core problem patterns: two pointers, sliding window, BFS/DFS on graphs, binary search variations, dynamic programming (1D and 2D), intervals, heaps, tries, topological sort, union-find, monotonic stack. Learning the patterns lets you recognize a new problem as a known shape. Memorizing specific solutions doesn’t scale.

3. Start with easy problems, finish each one

Early prep trap: jumping to hard problems, getting stuck, looking at solutions. That builds nothing. Do easy problems until you can solve them comfortably, then move to medium. Stop trying to get better by doing things beyond your current level.

4. Solve a problem three times

Attempt it fresh → read the solution → implement it from scratch, closed book, the next day. This three-pass approach turns exposure into retention. Just reading a solution teaches almost nothing.

5. Practice talking through the solution

Interviews score communication as much as correctness. Narrate your thinking: “My first thought is BFS because we need the shortest path. Let me consider edge cases first…” If you practice silent, you’ll interview silent, which reads as panic even when you’re not.

6. Use a timer, always

Real interviews are 45 minutes. Practice with a 35-minute timer using our countdown timer. Pressure changes everything — problems you can solve in an hour unstructured are very different from problems you can solve in 35 minutes with someone watching.

7. Do mock interviews, not just solo prep

Solo prep misses 40% of what makes interviews hard: the person on the other side, the pacing, the pressure. Pramp, interviewing.io, or a friend. Even 5 mock interviews add more than another 30 solo problems.

8. Study systems design proportional to target seniority

For senior+ roles, systems design is half the loop. Pick 2–3 canonical systems (URL shortener, Twitter feed, chat system, ride-sharing) and practice designing them in 45 minutes — capacity estimates, APIs, data models, scaling bottlenecks. “Designing Data Intensive Applications” is the one book worth reading for this.

9. Behavioral prep is not optional

Most engineers think behavioral rounds are easy and then tank them. Have 5–7 specific stories that cover: conflict, leadership, technical trade-offs, failure, and ambiguity. Use STAR structure (Situation, Task, Action, Result) and practice out loud. One great story covers three questions.

10. Review your own code under pressure

After each problem, re-read what you wrote. What was messy? Where did you hesitate? What edge cases did you miss? This self-review is where growth happens. Pair with our clean code guide for the style and structure side.

11. Sleep, exercise, and don’t grind the day before

The day before the interview, do one warmup problem and rest. Grinding hard problems 24 hours out makes you tired and shaky, not sharper. Cognitive performance is dominated by sleep and energy far more than by the marginal problem you did the night before.

12. Build a structured weekly plan

8–12 weeks of prep, 4–6 hours a week, is enough for most people with some background. Use our weekly planning guide to keep consistent progress. Skipping weeks is the #1 reason prep stalls.

Your first week of prep

Pick a target company. Identify the likely rounds. Spend one hour mapping the 15 patterns to example problems. Start with 3 easy problems, each done three times. Do one mock interview at the end of week two. Run that rhythm for 8 weeks. That’s the whole playbook.