Reach senior-level system design ability, usable both day-to-day at work and in interview/promo loops. The user has designed some systems but feels the fundamentals are thin — can produce a diagram, but can't confidently say why one design beats another, or defend the trade-offs under pressure. The mission is to close that gap: from "can draw a system" to "understands what makes a good one."
Success looks like
Given a vague design prompt, produce a complete design and run the standard framework (requirements → estimates → interfaces → data model → high-level → deep dives) without prompting.
For any design choice (cache, queue, shard, replica, CDN, event bus), state when it helps, when it hurts, and the cost — from reasoning, not recall.
Estimate scale credibly (QPS, storage, bandwidth, latencies) and sanity-check numbers.
Spot failure modes, bottlenecks, and single points of failure in a design and harden them.
Hold a senior system design interview round convincingly (for interview track).
Designs survive senior review at work; senior engineers stop finding holes the user missed.
Constraints
Time budget not yet defined — will find a rhythm (initially few hours/week).
Full-time software engineer, medior level, already has production design exposure.
Resume review will ground which gaps matter most for their actual trajectory (to be provided).
Out of scope
Cloud-provider-specific certifications and trivia (memorizing service SKUs).
Deep implementation details of a specific tech (e.g. Redis internals) unless needed for a trade-off.