Mobile tech lead on a 700K-MAU consumer fitness app: Flutter, app performance, LLM agents, and the teams that ship them.
Founding Engineer at Symmetry, a gamified fitness app ("Strava for the gym") with 700K+ monthly active users and 3M+ installs in 2026. I've led mobile across several squads, own Symmetry's AI coach and sit in the founders' leadership meeting.
I joined in January 2026 as a Junior Engineer, after freelance and open-source work going back to 2019. Since then I've been promoted five times in nine months: Mobile Engineer → Senior & Squad Lead → Tech Lead → Frontend Architect → Founding Engineer (October 2026). In 2026 I did more code reviews (142) and merged more PRs (465) than anyone else at the company.
Remote, Spain · rubenortiz.tech · LinkedIn · rortmarb@gmail.com
- Leading mobile: ~2.4× throughput without growing the team. While I was Tech Lead, merged mobile PRs per month rose ~2.4× (Jan–May vs Jun–Sep 2026), and engineers I mentored were promoted to Senior.
- AI coach, end to end (Python + Flutter): 79K users, 690K+ messages in its first four months. It's free for every user. Planner/executor routing cut latency by 60–77%, and consolidating 9 tools into 4 composable ones cut the agent loop rate from 65% to 13%. The backend and the app share a schema-first AsyncAPI contract.
- Cold start: 7.4 s → 294 ms (25×). I rebuilt app startup as a cache-first, four-phase init and deleted 4,000+ lines of dead code.
- Social feed: used by 1.5M+ people in 2026. I built it from scratch, then rebuilt it. Since January, likes have grown 3× and interacting users 5×.
- CI/CD: test suite 828 s → 197 s (~4×). I built CI/CD from scratch on self-hosted runners, with automated versioning and TestFlight releases. I also created a Debt Score metric: live debt fell 36% (591 → 381) in six weeks.
- Architecture for humans and AI agents. I led the move to a modular Flutter architecture (packages around a shared core), guarded by custom CI linters, contracts and tests, so AI agents can work autonomously under human review. The team kept shipping throughout the migration.
Side project: Nuvi
A native iOS app I built solo and launched on the App Store in September 2026, in English and Spanish. You scan a grocery barcode and get a yes or no for your fitness goal. It's built with Swift/SwiftUI, a Go + Elixir backend (Redis, ScyllaDB, AWS), App Attest and RevenueCat. It also has a 75-rule custom architecture linter that checks the whole repo in 4 s, and an LLM chat tested against a 119-scenario eval suite.
- Quimify (freelance, 2023–24): Flutter + Spring Boot. Moving data to a local database cut server load by 30%.
- NodeBot: a Node.js Discord bot I co-built (2019–22). It reached 2M+ users across 20K+ servers.
- Electrics-App: an offline Flutter app for designing and validating low- and high-voltage installations on site under Spanish regulations (REBT/RAT). It draws single-line diagrams and exports PDFs.
Most of my work is private: 2,600+ of my 2,800+ contributions in the last year.
Flutter · Dart · BLoC/Cubit · Clean Architecture · Swift/SwiftUI · Python · Go · Elixir · TypeScript/Next.js · Postgres/pgvector · ScyllaDB · Redis · AWS · Docker · GitHub Actions · RevenueCat · Stripe · Datadog · LLM agents and evals