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trying to make code better
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mystertaran/README.md

Szymon Tarańczewski

backend · frontend · observability · performance


I'm the kind of developer who opens the network tab before the design file. I like systems I can see into: traces that explain where the time went, caches that know when to step aside, and pages that render before you finish blinking.

I started out building UI components. Over time I took on the layers underneath them: server rendering, runtime, caching, telemetry and the infrastructure the whole thing runs on. Today I spend most of my time where a slow request turns into a good question.

What keeps me busy

Enterprise web platform. I'm a contractor on the global web platform of a large industrial company. It's one big SvelteKit monorepo that serves marketing pages, a help center, a product catalog and a B2B partner portal across dozens of countries and languages, including right-to-left. I joined to build CMS-driven components. Now I own performance, observability and much of the runtime underneath:

  • brought in OpenTelemetry end to end in server rendering, with telemetry config that changes at runtime without a redeploy
  • moved the app to Bun on Kubernetes with a custom multi-worker server, and found every place where Bun and Node quietly disagree
  • built a Redis/Valkey caching layer with an in-memory L1, pipelining, cluster mode and a latency-aware circuit breaker
  • shipped SSR islands for the global header, so the page hydrates only what needs to be interactive
  • hunted down memory leaks, trimmed the bundle with lazy component loading, and ran production performance audits (TTFB, LCP, payload, cache) that ended in fixes, not slides
  • made failures readable: precise upstream errors, request IDs that tie logs together, and pages that survive when one component fails

E-commerce in-house. I'm the developer and product owner for a fashion brand that sells in two markets. I build integrations between the store, order management, warehouse and accounting, plus a data layer that gives every dashboard one shared definition of revenue. The storefront is mine too.

Freelance. Custom storefronts and Shopify apps for brands, built pixel-perfect from Figma.

Just for fun. Small tools I build because I want them to exist, like an offline-first training app that runs on my phone every day.

What I enjoy

  • Following a span through three services and a queue until the bug has nowhere left to hide
  • Turning "it's slow sometimes" into a graph, a cause and a fix
  • Hydration puzzles: Svelte 5, web components, shadow DOM, all on one page
  • Workers, retries and idempotency, so nothing gets lost when the network doesn't cooperate
  • Front-ends that feel instant on a mid-range phone, not only on my machine

Toolbox

Frontend TypeScript · Svelte 5 · SvelteKit · React · Next.js · Tailwind · Web Components · Liquid
Runtime & backend Node.js · Bun · Python · PostgreSQL · Redis / Valkey · AWS Lambda
Observability OpenTelemetry · Dynatrace · GA4 / GTM
Build & infra Vite · esbuild · pnpm monorepos · Docker · Kubernetes · Google Cloud · AWS · GitHub Actions
Commerce & CMS Shopify (Plus, Functions, extensions) · Builder.io
Testing Vitest · Playwright

Currently tinkering with: SvelteKit 3, and AI agents that write specs before they write code.

Pinned Loading

  1. polubis/Dream-stack-for-React-dev polubis/Dream-stack-for-React-dev Public template

    TypeScript 27 4

  2. primavera-shop primavera-shop Public

    Modification of my existing project clothing shop Primavera using PrestaShop

    PHP 1

  3. my-blog-next-v1 my-blog-next-v1 Public

    JavaScript

  4. polubis/4markdown polubis/4markdown Public

    TypeScript 27 4

  5. monitor-useme monitor-useme Public

    Python

  6. omdb-example omdb-example Public

    TypeScript