Mobile App Developer · Senior · 10+ yrs

Mariam Sequeira

Principal Mobile Engineer / Mobile Lead

Lisbon, Portugal mariam.sequeira@proton.me +351 912 558 470 linkedin.com/in/mariam-sequeira-mobile github.com/mariamseq

Professional summary

Mobile engineering leader and architect with 12 years shipping apps used by tens of millions. Sets mobile architecture and release strategy across Flutter, React Native and native Swift/Kotlin, leads teams of 9–15 engineers, and ties technical decisions to business outcomes — crash-free rate, store rating, retention and revenue. Hired and grew mobile teams, drove a cross-platform consolidation saving crores annually, and mentors engineers into senior and staff roles.

22M+

App downloads led

₹3.4Cr

Annual delivery cost cut

Engineers led

Skills

Leadership

Mobile strategy & roadmapTeam building (9–15)Release strategyHiring & mentoringArchitecture review

Architecture

Modular mobile architectureOffline-first syncFeature flags & staged rolloutCross-platform (Flutter/RN)Performance budgets

Stack

FlutterDartKotlinSwiftSwiftUIJetpack ComposeReact NativeREST APIs

Platform

FirebaseFastlaneCI/CD (Bitrise, GitHub Actions)App Store / Play ConsoleCrashlytics & SentryOpenTelemetry

Work experience

Principal Mobile Engineer & Mobile Lead · Voyastay

Mar 2019 – Present

Lisbon

Lead a 14-engineer mobile org behind a travel-booking app with 22M+ downloads and 6M monthly active users across iOS and Android.
Defined the mobile architecture and a Flutter + native consolidation that retired two codebases, cutting feature delivery time 40% and saving ~₹3.4 crore/year in duplicated effort.
Owned the release strategy — staged rollouts, feature flags and automated regression — taking crash-free sessions from 99.2% to 99.93% and store rating from 4.3★ to 4.8★.
Built an offline-first sync platform for bookings that holds reservations and edits through connectivity loss, reducing support tickets 29%.
Hired 9 engineers and grew 3 into senior/staff roles; established the mobile architecture-review, performance-budget and on-call practices used company-wide.

Mobile Tech Lead · Cobalt Mobility

Jun 2015 – Feb 2019

Berlin

Led a team of 7 building a ride-hailing app (native Swift + Kotlin) scaled to 4M users across 18 cities.
Introduced CI/CD, Fastlane and automated UI tests, cutting release incidents 58% and enabling weekly store releases.

Senior Mobile Developer · Earlier roles — Nokia, Telefónica

2013 – 2015

Portugal / Spain

Built native Android and iOS apps across telecom and media products; promoted twice for delivery and technical leadership.

Education

M.Sc. Computer Science

2013

Instituto Superior Técnico, University of Lisbon, Lisbon

Certifications

Associate Android Developer

Google · 2018

Professional Scrum Master I (PSM I)

Scrum.org · 2017

Selected achievements

Cut mobile feature delivery time 40% and ~₹3.4 crore/year via a Flutter + native cross-platform consolidation.

Raised crash-free sessions from 99.2% to 99.93% and store rating from 4.3★ to 4.8★ through a staged-rollout release program.

Speaker, Droidcon Lisbon 2023 — "Offline-first booking at 6M MAU without losing a reservation."

Mentor at a women-in-tech mobile fellowship; advises 2 early-stage startups on mobile architecture and release strategy.

See the work in 3D

Explore Mariam's interactive WebGL portfolio — projects, skills and a way to get in touch.

Open the 3D portfolio