ISIMA

Engineering Manager at Facebook

Scaling the largest mobile codebases in the industry, and supporting their migration to modern languages.

Bootstrapped and grew a team of deep LLVM and Java compiler and programming languages specialists in London supporting the migration from Java to Kotlin and Objective-C to Swift, as well as building the codemodding and linting tools that help automatically delete dead code, migrate to the latest APIs and improve code quality, for all of our apps including Facebook, Instagram, WhatsApp, and Messenger.

Team achievements include:
- automating dozens of Facebook iOS's codebase modernisation efforts through clang-tidy codemods
- server-side clang-tidy linting reliability and coverage improvements preventing numerous production issues
- automatic restriction of Apple's IDFA APIs to ensure iOS 14 compliance across all of our mobile apps
- 30%+ Kotlin code size reduction through Redex optimisations enabling adoption in Facebook Android
- code size and build speed best practices program for Swift through AST lint rules

Facebook

Engineering Manager, Mobile Programming Languages

Supported the React Native Performance Team, from inception to success.

React Native is a big bet to reinvent the way we build mobile apps with an emphasis on iteration speed (reusing code and skills across web, iOS and Android, refresh rather than build & run), reliability (production hot fixes are possible) and app size (features can be loaded lazily). Improved performance 2.5x working with product, infrastructure and performance tooling teams. Now powering Facebook Marketplace, enabling the team to share code and skills across all their clients and deliver an experience that is indistinguishable from natively built product surfaces.

Grew the team from 8 in London to 40+ across London, New York, Menlo Park and Seattle. Pitched and supported building Hermes VM, a custom JavaScript VM build from scratch to address embedded JS performance challenges: tiny binary footprint, pre-build compact bytecode, moving + compacting GC and custom fast paths for React.js, along with all the performance and debugging tools we needed.

React Native has also been extremely successful in the industry making web and mobile developers more productive across platforms, topping the Github's charts (#2 in 2018), powering many apps like AirBnB and Shopify, and being officially adopted my Microsoft as an official Windows target (including Hermes VM).

Engineering Manager, React Native Performance

Joined the Facebook London site when we were 50 people, tech lead for iOS permalink and comments, the most visited product surface after Newsfeed:

- 70% faster comments load, increasing engagement and retention
- led comments data model re-architecture, decoupling fetch from display
- led iOS 64 bit transition: 250 libraries and 10 apps transitioned in 4 months
- Facebook Apple Watch app prototype in Cupertino ahead of the 2014 Keynote
- supported app-wide navigation API re-architecture, decoupling products from each other
- onboarded, supported and mentored a team of 4 engineers
- transitioned into an official manager role towards the end of 2014
- iOS interviews and training other interviewers, second iOS interviewer in London
- installed the London office burger culture

iOS Engineer, Newsfeed

Freelance iPhone & iPad development.

Working with New York based PrePlay on all their amazing MLB, NHL and NFL live prediction games, Paris based Joshfire on their innovative app factory and L’Équipe Adrenaline app, and Lyon based Inook on a beautiful interactive Burgundy wine showroom app.

WWDC 2013 attendee.
NSConference 2013 attendee.
NSConference 2012 attendee and blitz talk speaker.
Regular Cocoa Heads Lyon speaker and attendee.

teapot apps

Freelance Senior iPhone & iPad developer, Founder

Senior iPhone Software Engineer managing development teams.

Lead developer on the french major financial newspaper Les Echos apps for the iPhone, iPad, Android, Windows Phone and webOS tablet. Architect, build and ship a new project every two months. Train junior iOS engineers. Build the high performance iOS PDF reader component used in all the 5+ Visuamobile newspaper apps. Build the social sharing framework used in all Visuamobile apps. Develop and maintain the automated iPhone apps build process. In-house Web Services expert.

WWDC 2011 attendee.
Regular Cocoa Heads Paris attendee.

Visuamobile

Senior Lead iPhone Software Engineer

In charge of the d2 / 2big / 5big Network NAS products system, configuration backend and setup Web interface.

Linux system architecture and fully integrated build system development, release management. Python backend system architecture and implementation, migrating from an obsolete C++ / dbus architecture. Leading a team of 10 engineers to build the backend system. Ajax Web system setup frontend in Javascript and GWT. Two-folds system performance improvement on RAID rebuild times (a critical step in setting up a NAS system).

Attended WWDC 2008.

LaCie

Embedded Linux System Lead Software Engineer

8 months internship at the Siemens Corporate Research center in Princeton, NJ, USA.

Explore emerging Ajax technologies to update industrial control panel user interface. Understand the architecture of a 1M+ lines of code C++ project, define ways to port the GDI interface to HTML / JS. Prototype and develop a working solution. Present Ajax technologies in front of all the research center Siemens employees.

Rated Very Good by the school's jury. Highly appreciated by the Siemens team. I was offered a position in Princeton and in Germany at the end of this internship.

Siemens Corporate Research

C++ / Web Software Engineering Intern

Project Lead and Developer, Treasurer at the school's junior company run by students.

Creation of the Auvergne Management University Website, managing a 5 persons team at ISIMA’s Students Service Company Im@ge during my studies. Technologies involve PHP 5 / Symphony, MySQL 5, XHTML / CSS2, Flash and XML technologies. Successfully meeting a tight release deadline through direct client relation.

Im@ge ISIMA

Student Software Developer and Treasurer

6 month internship at Siemens AG in Karlsruhe, Germany within a 4 persons team.

Development of a portable C++ stream and object-oriented communication library. Using C++, C sockets, C++ STL streams and CMake, documentation generated with Doxygen and LaTeX. Cross compilation on Windows and Linux with CMake.

Rated Very Good with congratulations of the school's jury. Highly appreciated by the Siemens team, which provided me with a further internship offer in the US.

Frédéric Sagnes