Senior Fullstack Engineer

Why a trading platform can't ship the free TradingView widget, and the full pipeline from tick to candle: a custom datafeed, a Web Worker fetching tens of thousands of candles, a backend cooking candles in Node memory — then both sides optimizing together around one insight: a closed candle is immutable.

What tRPC actually is, and why a NestJS + React monorepo dropped every REST controller to run on it: the express adapter, a JWT-authenticated context, a procedure chain, router factories co-located with services, React Query hooks generated straight from router files — and the price you pay.

I've sat on both sides of the Tech Lead interview table: people usually fail the leadership & behavioral round not for lack of skill, but because their stories lack context and lack the cost. Covers telling STAR stories with numbers, ADRs and trade-offs, handling disagreement, managing tech debt, mentoring mid to senior, code review culture, negotiating scope, incident ownership, and the questions worth asking back.

The frontend system design round for a Lead role: when NOT to use micro-frontends, Module Federation vs iframe vs route-based, monorepo with build cache, design system governance, data fetching strategy, strangler migration and observability — through a case of 6 teams, a 25-minute build and releases stuck in a queue.

Session or JWT, refresh token rotation, cookie flags, CSRF, XSS and CSP, OAuth2/OIDC with PKCE, the BFF pattern: seven Auth & Security questions I often see in the Senior Fullstack round, with Go and React examples.

What is the browser actually doing underneath the framework? Six groups of browser-internals questions I often see in the Senior Frontend round: the critical rendering path, layout/paint/composite, layout thrashing, streaming SSR and hydration, memory leaks, debugging with DevTools, and optimizing INP.