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Senior SWE interview prep — system design, coding patterns, flashcards, request traces
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L5 / L6 / staff prep<br>Practice rounds<br>Interview prep<br>Most of Semicolony is reference material — long-form deep dives you read when you want to understand something. This section is the opposite. Pick a flow, set the timer, work through it the way you'd work through an actual interview round. Every flow links back into the deep material when you need to look something up.<br>Four flows are live: a 45-minute system-design round with fourteen canonical prompts, a hundred interview flashcards across six categories, a coding pattern drill covering twenty patterns, and a request-trace exercise for networking rounds. Supporting material covers the day-of warm-up, company loop shapes, a self-grading rubric, and L5 vs L6 vs staff differences.
FOUR · DRILLS0145 minSYSTEM DESIGN0215 minCONCEPTS0345 minPATTERNS0425 minTRACEfour drills, one clock each — all live
Live flows<br>01<br>System design · 45 min<br>The 45-minute system-design round.<br>A randomised prompt from the system-design playbook — URL shorteners, news feeds, rate limiters, ride-matching, object storage. A clock counts down 45 minutes, divided into the seven phases of a real interview: clarify, capacity math, API + schema, high-level architecture, deep dive, scaling + failure modes, follow-ups. When the timer ends, the reference solution from the playbook unlocks for comparison.<br>Start the round → 14 prompts·45 min·self-scored
02<br>Concept drill · 15 min<br>Interview flashcards.<br>A hundred cards across six categories: distributed systems (consensus, CRDTs, quorums), databases (LSM, MVCC, vacuum), networking (TCP, HTTP/2, BGP), operating systems (mmap, page faults), system design (queues, caching), and languages (goroutines, GC, the event loop). Filter by category. Spacebar to reveal, arrows to navigate.<br>Open the flashcards → 100 cards · 6 categories·~15 min per pass·keyboard-driven
03<br>Coding patterns · 45+ min<br>Coding pattern drill.<br>Pick one of the twenty canonical coding patterns — two-pointers, sliding window, BFS, DFS, backtracking, DP, greedy, heap, monotonic stack, union-find, trie, topological sort, bit manipulation, linked list, tree DP, graph algorithms, math, binary search, recursion, hash map. Three problems per pattern at escalating difficulty (easy, medium, hard), each with a reveal-able approach hint and a LeetCode link. Pattern-wide timer.<br>Open the drill → 20 patterns·60 problems·time-boxed
04<br>Request trace · 25 min<br>Trace a request, name every layer.<br>The "what happens when you press Enter" warm-up. Six scenarios — curl to an EC2 instance, browser to a CDN, signed S3 URL, SSH tunnel to managed Postgres, gRPC through Istio, WebSocket through an L7 LB. Write your trace freehand (saves to your browser), then reveal the canonical step-by-step trace with deep-dive links.<br>Open the drill → 6 scenarios·~25 min·self-scored
Supporting material<br>Day-of<br>Warm-up checklist<br>Printable checklist for the night before, morning of, between rounds, and after the loop. Plus a one-page trade-offs cheat sheet.<br>Open → Companies<br>Company loop guide<br>FAANG-tier loop shapes — Google, Meta, Amazon, Apple, Netflix, Stripe. Round-by-round breakdown, quirks, what they're grading on.<br>Open → Self-grade<br>Feedback rubric<br>24-point self-scoring rubric across the seven phases. Deep dive is double-weighted. Calibrated bands map your total to a hire / no-hire reading.<br>Open → Levels<br>L5 vs L6 vs Staff<br>What actually changes between senior, staff, and principal IC loops. Round-by-round delta. Common downlevelling signals.<br>Open →
Who this is for<br>Software engineers with three to ten years of experience interviewing for L5 / senior, L6 / staff, or equivalent IC roles at FAANG-tier companies and the hundred or so other companies that run the same kind of loop. The flows are biased toward the system-design round and the distributed-systems concepts round, because those are the two that most candidates with strong fundamentals still find hard. Coding rounds get less attention here — there are better resources for raw LeetCode reps elsewhere.<br>If you are interviewing for an L4 or junior role, the flows still work — the system-design round is the same shape, just shallower. The flashcards and pattern drills are level-agnostic. If you are interviewing for a principal / staff+ role, the flows are a warm-up; the real prep at that level is mentoring junior engineers through their interview prep and remembering what fundamentals look like.
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