Iurii Uses: #TypeScript

kri.rocks – Booking Website and Online Scheduling SaaS for Beauty Businesses

Vertical SaaS that gives a salon, barbershop or solo beauty specialist their own booking website in minutes.

polytypo.dev – Locale-Correct Typography Engine and Spec

Open-source spec and engine that turns straight quotes, hyphens and three dots into curly quotes, dashes, ellipses and no-break spaces for 10 locales.

halloween.js – Zero-Dependency Halloween Effects for Any Website

Zero-dependency Halloween corner decorations and ambient effects – one script tag or npm install, class-driven, seasonal by default, under 10 KB gzipped.

n8n Verified Community Node – EU VAT Validation in Workflows

Verified n8n node for VIES VAT validation and EU rate lookups in a workflow, so onboarding or invoicing acts on a real VAT number, not a well-formed one.

pi-pi.ee – Live Custom-Colour Preview

Recolour a product photo to any colour in the browser, instantly – an SVG duotone filter tints transparent master images on the fly.

pi-pi.ee – B2B Deal & Document Portal

Internal sales portal that turns a wholesale deal into its full trade paperwork from one form: pro forma, contract, commercial invoice, packing list, CMR.

vatnode.dev mcp – Official MCP Server for EU VAT Validation

Open-source MCP server that lets Claude Desktop, Cursor and other MCP clients validate EU VAT numbers and look up rates directly in chat.

HTPBE.TECH – Internal Admin Dashboard

Role-gated admin dashboard for the HTPBE? SaaS platform – real-time KPIs, per-user quota tracking, and a zero-dependency bar chart.

HTPBE.TECH – PDF Verification Workflow Animation

Looping SVG animation illustrating a PDF verification pipeline – document stack, cloud processing, and green/red folder sorting.

pi-pi.ee – i18n B2B Presentation PDF Generator

On-demand PDF presentation generator for 31 European markets – one codebase, one URL pattern.

eu-vat-rates-data – Free & Open-Source EU VAT Rates Dataset

Free, open-source EU VAT rates for all 27 member states + UK. Published as native packages for npm, PyPI, Packagist, Go, and RubyGems.

vatnode.dev – EU VAT Validation API

Developer-first SaaS API for EU VAT validation via VIES with Redis caching, change monitoring, and webhook notifications.

pi-pi.ee – B2B E-commerce for Waterless Urinal Systems

i18n B2B e-commerce platform for waterless urinal products across 32 European countries with automated VAT handling, PDF invoicing, and CRM integration.

pikkuna.fi – i18n RAG AI System

RAG system on OpenAI and Upstash Vector in 30 languages, with a streaming chatbot and hybrid search (semantic + keyword).

PostNord Shipping Automation

Automated PostNord label generation for 20–50 daily shipments, replacing 5–7 minutes of manual portal work per order.

pikkuna.fi – Real-time SVG Product Configurator

Client-side SVG configurator with live preview for designing vinyl curtains and roofing panels.

pikkuna.fi – E-commerce for Vinyl Curtains & PVC Products

E-commerce platform with 30 locales, product configurators, AI chatbot, and fully automated order flow: Stripe → Zoho CRM → Airtable → Mailgun → PDF.

HTPBE.TECH – Has This PDF Been Edited?

SaaS platform for PDF authenticity verification with a public REST API.

Prevent double booking in PostgreSQL without UNIQUE or EXCLUDE: advisory locks, an overlap check, and when EXCLUDE is the right choice.

Booking slots across daylight saving time: why isValid misses skipped times and why a pinned version cannot resolve autumn ambiguity.

Race condition testing with real PostgreSQL: readiness gates, observed lock waits, provider stubs, and the false confidence a timed assertion can give.

Why a Node worker writes every confirmed order to Airtable alongside the primary database, and what belongs in that snapshot and what doesn’t.

Building the vatnode MCP server meant deciding whether format-checking and live VIES validation should be one tool or two.

polytypo’s typography engine is a nine-rule pipeline that locates and rewrites text without ever building or reprinting an AST.

Why a Next.js e-commerce project fetches EUR/VAT reference data once per build instead of once per request or never.

How to call a logistics provider’s API from an order-processing worker, and why some booking APIs answer immediately and others don’t.

How to wire an external accounting or bookkeeping API into a payment flow, and why the call belongs in the queued worker, not the webhook handler.

Readable Sentry stack traces from a self-hosted Next.js standalone build: instrumentation.ts, withSentryConfig, source map upload, and verifying symbolication.

halloween.js adds Halloween decorations to any website – one class flips them on, and a real-calendar season window turns them off automatically.

Structured logging in Next.js with pino: JSON to stdout, a per-request x-request-id, a wrapper that logs method/path/status/latency, and no secrets in logs.

Build a type-safe content layer with Velite: Zod schemas for MDX and JSON, computed fields, one typed import, and a related-posts codegen step.

WebSocket reconnection for production: heartbeat dead-connection detection, exponential backoff with jitter, resubscription, and message replay.

Batch PDF generation in Node.js without OOM: concurrency limits, back-pressure, releasing renderers between docs, and why Promise.all(map) fails at scale.

B2B quote-to-order flow in Next.js: RFQ → quote → order state machine, per-deal line items, guarded transitions, and quote conversion without data drift.

API key management for a public SaaS: hashing keys at rest, prefix + last-4 display, fail-closed validation, and revocation.

Prevent overselling under concurrent checkouts: reservations vs hard decrements, SELECT FOR UPDATE, deadlock-safe multi-line carts, and the payment window.

Gated B2B pricing in Next.js: per-account price lists and server-side access control so prices never leak to crawlers.

Subscription billing edge cases Stripe glosses over: proration, dunning, the state machine, cancellation timing, refunds, VAT, and webhook ordering.

Webhook security past the signature: replay attacks, payload trust, DoS, IP allow-listing, and secret rotation – what verification does not protect.

Feature flags without LaunchDarkly: a Postgres-backed, ~100-line system with deterministic percentage rollout, per-tenant overrides, and caching.

Semantic search for internal docs with Postgres and pgvector: chunk, embed, and query by meaning so people find the right document, not the exact words.

Idempotency key API design: make POST retries that don’t double-charge – Postgres key table, ON CONFLICT claim, response replay, TTL, edge cases.

Stripe to Mollie migration in production: mandates instead of Subscriptions, thin webhooks, no proration, no portal, no Tax. What you rebuild yourself.

Build an internal CRM on Supabase: schema, RLS policies, Next.js App Router frontend, realtime subscriptions, and an honest look at where the weekend ends.

Multi-tenant SaaS database design: shared schema with RLS, schema-per-tenant, and database-per-tenant – trade-offs, real pitfalls, and when to use each.

Production healthcheck endpoints: liveness vs readiness probes, dependency checks with timeouts, 200 vs 503 logic, Docker and Kubernetes config, and security.

PostgreSQL production patterns: UUID v7, soft deletes, RLS for multi-tenant SaaS, partial and covering indexes, PgBouncer pooling and migration discipline.

BullMQ vs pg-boss vs node-cron for Node.js background jobs. Trade-offs between Redis and Postgres queues, retries, deduplication, and production monitoring.

JWT vs sessions vs OAuth for SaaS: token invalidation, mobile clients, refresh token rotation, and a decision matrix to pick the right auth pattern.

AI document processing in production: full PDF pipeline – OCR fallbacks, structured output, validation, cost at scale. Beyond naive GPT calls.

Add AI to an existing product without a rebuild. Three integration patterns, how to pick the right one, and what production-ready AI actually demands.

Use linkinator to catch broken links before production: local URL rewriting, --silent flag, GitHub Actions, and false positives from LinkedIn and GitHub.

Agency codebase handover checklist: first 48 hours, security triage, architecture mapping, and how to write a takeover assessment. Practical guide.

Data format comparison: JSON, YAML, TOML, CSV, Protobuf, MessagePack – tradeoffs, performance, and a decision framework for production systems in 2026.

Build a React product configurator with Zustand, DaisyUI, Motion animations and a live SVG preview – architecture, pricing logic, and performance patterns.

Real-time Next.js admin dashboard: TanStack Query polling, Zustand for filter state, Sentry error boundaries per panel, and a zero-dependency bar chart.

IndexNow implementation for Next.js: key generation, TypeScript client with retries, GitHub Actions workflow, and pitfalls that break submissions silently.

GDPR-compliant analytics with Umami: no cookies, no consent banner, self-hosted or cloud – and when server-side GA4 is still the right call for EU products.

PostNord API and Zoho Desk automation for EU e-commerce, and the gotchas to watch for: 200 OK empty arrays, EU data center URLs, token caching.

Migrate middleware.ts to proxy.ts in Next.js 16 without breaking auth.

Production transactional emails with React Email and Resend: PDF invoices via react-pdf, Vercel Blob temporary storage, and BullMQ Stripe webhooks.

Self-host a Node.js API on a €6/month VPS: Caddy reverse proxy, Docker Compose, zero-downtime deploy script, and GitHub Actions CI – complete production setup.

How to publish one dataset to npm, PyPI, Go Module, RubyGems, and Packagist with GitHub Actions – architecture, versioning, and per-ecosystem gotchas.

Next.js view counter with Upstash Redis over HTTP: atomic INCR, Edge Runtime for zero cold starts, React Strict Mode fix, and slug namespace gotchas.

React masonry layout that keeps left-to-right card order with variable heights – where the popular CSS column-count trick silently breaks.

UUID v7 vs v4 in PostgreSQL: why random UUIDs fragment B-tree indexes, how UUID v7 fixes it, benchmarks at 5M rows, and Drizzle ORM migration steps.

CSS SVG animation with pure @keyframes: sync multiple tracks, fix the SVG transform override trap, and build smooth loops without GSAP or Framer Motion.

Next.js dynamic OG images with Satori: why opengraph-image.tsx hangs Turbopack at 400% CPU, how API routes fix it, plus WOFF2 and Twitter card gotchas.

E-commerce order automation that cut 160+ hours/month of manual work to zero: Stripe webhook to VAT invoice and tracking in under 2 minutes.

EU VAT validation in Next.js: VIES caching with Redis, three-state results, reverse charge logic, and audit logging – what actually works in production.

40+ point production SaaS checklist: auth, Stripe billing, PostgreSQL, rate limiting, email, monitoring, and security – with honest 8-week build estimates.

Stripe webhook production architecture: idempotency keys in PostgreSQL and Redis, a BullMQ queue, and signature verification in Next.js App Router.

Technical SEO built into Next.js: server-side rendering, dynamic meta tags, JSON-LD structured data, and automatic sitemap generation – no plugins, just code.

Detect tampered PDFs using xref table analysis, metadata mismatches, orphaned objects, and font changes – 7 forensic markers explained with TypeScript code.

Next.js i18n for 30 languages in production, not a 2-locale demo: next-intl routing, type-safe translations and hreflang at scale.

RAG chatbot for e-commerce: resolve 70% of support queries across 25 languages – ingestion pipeline, hybrid search, confidence thresholds, and streaming UI.

Redis rate limiting for APIs: sliding window ZADD with Lua atomicity, in-memory fallback, multi-tier limits by IP and API key, and clear response headers.

Server-side GA4 and Meta CAPI in Next.js to recover the 30–50% of conversions adblockers and iOS hide from you.

Puppeteer vs @react-pdf/renderer for Node.js PDF generation, decided by production use, not benchmarks.

Turborepo monorepo with Next.js and Hono, sharing one set of TypeScript types across frontend and backend.