The 90-Day Coding Interview Prep Plan (For Engineers With a Full-Time Job)
A 90-day coding interview prep schedule for working engineers: three 30-day phases, a weekly template, review cadence, and when to start mock interviews.
- leetcode study plan
- software engineer interview prep
- DSA roadmap
- mock interview schedule
Short answer: with a full-time job, plan on about 90 days at 6 to 8 hours a week. Spend the first month learning core patterns, the second month drilling your weakest pattern tags at medium difficulty, and the last month doing timed mock interviews where you talk while you code.
Most coding interview preparation plans are written for someone with eight free hours a day. This one assumes you have a job and maybe kids, and that you will lose a week somewhere to an outage or a cold. It is built to survive that.
If you have not read how to think out loud in a coding interview, skim it first. This schedule assumes you practice explaining your solutions from day one, not as a final polish.
What you should be able to do on day 90
- Read an unseen medium problem, propose two approaches, and implement one in 25 to 35 minutes while narrating.
- Have done two or three voice or human mocks a week for the final month. AI vs human mock interviews covers how to mix them.
- Keep a review deck of roughly 40 problems you can re-solve cold.
- State time and space complexity without stalling. The time complexity guide pairs well with weeks 5 to 8.
Phase 1 (days 1-30): patterns, not trophies
The goal is to see each core pattern once and understand why it works. Streaks and problem counts do not matter yet.
| Week | Focus | Problems to start with |
|---|---|---|
| 1-2 | Arrays, hash maps, two pointers | Two Sum, Container With Most Water, and the Two Sum walkthrough |
| 3 | Stacks, queues, monotonic stack | Valid Parentheses, Daily Temperatures |
| 4 | Linked lists, fast/slow pointers | Linked List Cycle, Merge Two Sorted Lists |
Weeknights: 45 to 60 minutes of focused solving, then 15 minutes recapping out loud: what was the pattern, and what in the prompt should have tipped you off?
Weekends: one 2-hour block, plus one problem with a hard 35-minute cap.
Do not judge yourself by solve count. One problem you can explain beats three solutions you copied from the discussion tab.
Phase 2 (days 31-60): medium density and weak tags
The goal is to move from "I've seen this" to "I can execute this with a clock running."
- Tag every solve:
two-pointer,binary-search-on-answer,BFS,topo-sort, and so on. - Each week, pick your two worst tags and schedule six problems across them.
- Add one hard problem each weekend. The point is practice at staying organized when you are not sure of the answer, not bragging rights.
After each session, write one paragraph deriving the Big-O of that day's hardest problem from its loop structure. If you can only recite it, you will stall when an interviewer asks why.
Phase 3 (days 61-90): interview fidelity
The goal now is to match the format, not just the content.
- Do two full mock interviews a week, with a voice AI interviewer or a strong peer. You want interruptions, hints, and a clock. Read what FAANG interviewers score so you know which signals you are producing.
- Alternate interviewer styles: one strict and quiet, one that coaches.
- Cut new problems to about 40% of your time. The other 60% goes to review, weak tags, and explaining solutions out loud.
A weekly template you can copy
| Day | Activity |
|---|---|
| Mon | 2 mediums, each followed by a spoken walkthrough |
| Tue | 1 medium + 1 review problem solved blind |
| Wed | 2 problems from your weakest tag |
| Thu | 1 hard (45-minute cap) + a written post-mortem |
| Fri | Light review or rest |
| Sat | Mock interview + 1 easy medium to cool down |
| Sun | Prune and add to the review deck |
Move days around to fit your energy. Showing up five days a week beats one heroic Saturday.
Burnout guardrails
- Cap new problems at three on work nights.
- If you miss a week, shrink the plan. Do not try to make up for it by doubling the next week; that is how people quit.
- Protect sleep before an interview week. Tired candidates recover from small mistakes badly, and recovery is something interviewers notice.
FAQ
How many LeetCode problems is enough?
There is no magic number. For most mid-level roles, 120 to 180 problems you have actually understood, with spaced review, will serve you better than 400 you rushed. "Understood" means you can re-derive the approach and its complexity a month later.
Should I use a premade list?
A list is useful for structure in the first month. After week four, your weak tags should decide what you practice next, not the list order.
Where does TechInView fit?
DSA practice on TechInView is free, so it works in phases 1 and 2 for solo reps on the practice set. The 45-minute voice interview fits phase 3, when you need to talk and code at the same time under a clock. Start practicing when you are ready.
Summary: run coding interview preparation in three 30-day phases: patterns, then weak-tag density, then timed mocks. Practice explaining your work throughout, and treat the final month like the real interview: timed, spoken, and honest about which tags you still avoid.