Interview Prep — SDE2 → Senior (3 weeks)

A focused 3-week plan to switch jobs as an SDE2 with 5.5 years of experience, covering DSA and system design (HLD + LLD). Runs Wed 21 Oct → Tue 10 Nov 2026.

Repo structure

.
├── README.md                     ← you are here: plan + how to use the repo
├── dsa/
│   ├── PROBLEMS.md               ← day-by-day problem list with LeetCode links
│   └── solutions/                ← (add) your solutions, one file per problem
├── system-design/
│   ├── CRASH_COURSE.md           ← principles, patterns, top 16 problems, reading map
│   └── notes/                    ← (add) one file per design you practise
└── tracker/
    └── interview_prep_tracker.xlsx

Why this shape

At 5.5 YOE, interviewers expect DSA to be solid and system design to be strong, with you driving the discussion. Most loops also include a low-level design or machine-coding round, so LLD is folded into the design track. Behavioral and project deep-dives get a slot in Week 3 because they are often what separates SDE2 from senior offers.

Week 1 — Rebuild fundamentals

Patterns: arrays/hashing, two pointers, sliding window, binary search, stacks, heaps, linked lists, trees. Design: the core building blocks, then the first two full designs.

Week 2 — Harder patterns and classic designs

Patterns: graphs, union-find, Dijkstra, dynamic programming, backtracking, tries, intervals, greedy. Design: one classic HLD problem per day, plus the first LLD problems.

Week 3 — Simulate interviews

Mixed timed DSA, the remaining HLD problems, LLD in 60–90 minute sittings, three mock interviews and behavioral prep.

Daily routine

1. DSA first while you’re fresh. Time-box each problem to 25–30 minutes; if stuck, read the approach and re-solve it yourself 2 days later (the tracker sets the redo date automatically).
2. Log every miss with the pattern and why you missed it. The mistake log is worth more than the problem count.
3. Design out loud with a 45-minute timer using the 7-step framework, then compare against the book chapter and note what you missed.
4. Update the tracker — status, actual hours, notes — before you stop for the day.

Habits that make the difference

• ~80 well-understood problems beats 200 rushed ones. Easy problems are warm-ups at this level: if the solution is obvious, skip or code it fast.
• Lead with clarifying questions in both DSA and design rounds; it’s a strong senior signal.
• In design rounds you’re graded on trade-off reasoning and driving the conversation, not on a “correct” diagram.
• Mocks expose gaps faster than anything else — do at least three in Week 3.

Progress

• Week 1 — fundamentals (50 problems, 6 HLD topics, 2 designs)
• Week 2 — patterns & classic designs (38 problems, 7 designs, 2 LLD)
• Week 3 — interview simulation (17 problems, 3 designs, 3 LLD, 3 mocks)
• All Grind 75 problems attempted
• Final-day checklist in the crash course complete

Resources

• Grind 75 — the DSA backbone
• System Design Interview Vol 1 (Alex Xu; private PDF, opens for you only) and Vol 2 (Alex Xu & Sahn Lam) — worked design walkthroughs
• Designing Data-Intensive Applications (Martin Kleppmann) — selective reading on replication, partitioning, consistency
• Pramp, interviewing.io, or peers — mock interviews

Vol 1 chapter numbers are checked against the book. Vol 2 chapter numbers and LeetCode links were written from memory; verify them and fix any link that 404s.

Using this repo

Tracker: open the tracker page on the live site. Progress saves in your browser as you click. To keep it in this repo and sync across devices, click Local only → Connect GitHub and paste a fine-grained token with Contents: read and write on this repo only; progress is then saved to progress.json on the progress branch (separate from main, so saves don’t rebuild the site). Problems and days come from tracker/data.json; after editing the plan or problem list, run python3 scripts/build_tracker_data.py and commit.

Serve it as a site with GitHub Pages:

1. Push the repo to GitHub.
2. Go to Settings → Pages, set Source to Deploy from a branch, pick main and / (root), and save.
3. After a minute the site is live at https://<your-username>.github.io/<repo-name>/. This README becomes the home page, and the links to the other .md files work as pages.

git init
git add .
git commit -m "3-week interview prep plan"
git branch -M main
git remote add origin https://github.com/<your-username>/<repo-name>.git
git push -u origin main

Keep the repo private if you’d rather not share your progress; GitHub Pages on private repos needs a paid plan, so make it public if you want the free site.