Koray E.

hello@koray.onlgithub.com/koraybey

I build cross-platform products that run everywhere, from smartphones to bare metal. Over a decade as technical lead and IC, I get new ventures to market, untangle systems under scale, and keep teams shipping through tight feedback, predictable releases, and metric-driven decisions.

Experience

Shio Capital
Berlin, Germany
Various Technical Roles May 2020 - Jun 2024, Jan 2025 - Ongoing
Private equity investing in early-stage companies and scale-ups. Leading in-house incubation as IC and technical lead, shipping ideas from prototype to production.
Mmaah
Berlin, Germany
Lead Developer Jan 2025 - Ongoing
Fast-growing Korean QSR. Built mobile and embedded stack including scan-order-pay flow via App Clip and Rust printer service to convert anonymous deliveries into identified, enrolled customers.
  • Shipped gzip bundle with runtime decompression; ~7 MB smaller at ~50 ms startup cost
  • Built Rust printer service on NixOS/RPi; QR codes enable order attribution and loyalty
  • Created Lightspeed proxy with caching; TTFB ~100 ms vs ~7 s from vendor API
  • Developed live order tracking by bridging 3 vendor APIs, integrating kitchen automation and POS
  • Built functional transform package to normalize vendor schemas and prevent errors
TypeScriptRustReact NativeNixOSdrizzleworkerdCloudflareEffectHonoZustandTamaguifastlaneVitestStripe
MEMBER
Berlin, Germany
Co-founder, Product & Technical Lead May 2020 - Jun 2024
Cross-platform community toolkit spanning Chromium start pages and React Native app. Raised $2M with Barça Vision partners. Led product and co-led engineering from concept to production.
  • Led and mentored 17-person product and engineering team
  • Set up CI/CD with checks, tests, scaffolding, and automated versioning
  • Shipped ~450 releases and ~250 features on two-week cadence
  • Built onboarding with ~25% referral activation and ~60% monthly retention
  • Built framework for auto-generated landing pages; ~40% pageview-to-install rate
TypeScriptReact NativeReactExpressGraphQLTamaguiStorybookZustandfastlaneTerraformFirebaseChrome Extensions
Complori
Berlin, Germany
Technical Lead, Contract Jul 2024 - Jan 2025
K-12 edtech platform. Stabilized 4-year-old codebase, cleared technical debt, added telemetry and testing, hardened serverless functions, and mentored the team.
  • Led development and maintenance of two Next.js platforms with 5-person team
  • Optimized trial flow; conversion from ~17% to ~25%, a ~47% lift
  • Built subscription flow; premium share ~50% with higher LTV
  • Migrated to Google Cloud with Terraform; added CI/CD, logging, and recovery
  • Raised test coverage from ~0% to ~31%; near-zero failures in critical functions
  • Added caching and lazy loading; checkout and subscription pages 3× faster
TypeScriptReactReact QueryNext.jsKoaTailwindStorybookMongoDBTerraformGoogle Cloud
Bilemezsin!
Istanbul, Turkey
Founder, Product & Technical Lead Jun 2016 - Jan 2020
Social predictions app where users discuss news, make predictions, and redeem prizes. Built from scratch; became 2017 chart-topper in Turkey with ~1M installs, ~300K MAU, 4.8/5 stars (~110K ratings).
  • Raised $430K and built 20-person startup
  • Shipped Cordova and React apps with PHP backend
  • Added gamification and Redis leaderboards; 45%/25%/15% D1/D7/D30 retention
  • Automated user acquisition; ~600K installs at $0.10 CPI
  • Ran ASO with A/B tests; store conversion from ~15% to ~60%, top-ten ranking
  • Built auction marketplace and distributed ~10K rewards
JavaScriptReactApache CordovaPHPReduxRedisMySQLDigitalOcean

Projects

hono-tanstack-query

TanStack Query wrapper for Hono RPC endpoints.

TypeScriptTanStack QueryReact
ch9329-rs

Rust drivers for CH9329 keyboard emulation chips.

Rust
Medkai

Mobile scanner and cabinet for German meds, with answers on demand.

TypeScriptdrizzleworkerdOpenNextReactRustCloudflare WorkersVitestPlaywrightNixOS