Mojtaba Koosej

Projects

Snap Inc.

  • Cross-Platform Networking & Dependency Ecosystem: Maintained and optimized Snap's foundational native networking core (Chromium networking stack, gRPC, Protobuf, and BoringSSL) powering critical mobile infrastructure for 900M+ MAU. Developed an AI-assisted migration system for large-scale open-source software (OSS) dependency upgrades to automate patch migration and ABI compatibility validation.
  • Media Scheduling & Playback Framework: Architected Snapchat's cross-platform Media Scheduling Framework, dynamic caching systems, and network prioritization heuristics to intelligently allocate bandwidth across Messaging, Stories, and AR workloads, significantly improving startup latency and playback stability on constrained networks.
  • Network Quality Estimator (NQE): Designed an internal low-latency prediction model using low-level telemetry from the native networking engine to accurately forecast real-time network conditions (within sub-10ms error margins) for workloads where adaptive bitrate streaming was unavailable.
  • Cross-Functional Carrier & Cloud Infrastructure Initiatives: Served as the engineering lead for global network performance, designing carrier-level observability data pipelines (BigQuery, Airflow, Flink, Prometheus). Partnered directly with cloud providers (AWS, GCP) and telecom carriers (AT&T, Verizon, Telcel) to mitigate regional routing instability, resolve QUIC throttling, and restore zero-rating configuration failures.
  • Native Android Networking Integration: Acted as the technical lead and owner for native C++ networking and gRPC architecture across Android, iOS, and WebAssembly. Optimized JNI boundaries, memory footprints, socket lifecycles, and retry strategies, reducing Android memory-pressure crash rates by 5% and time-to-first-byte by 80ms.
  • Developer Infrastructure & Mobile Testing Frameworks: Scaled internal developer productivity by delivering the first large-scale automated UI test harness into Snapchat's primary CI workflow and designing a unified cross-platform schema for test collection analytics. Developed an in-house iOS crash reporting SDK to replace third-party tooling and enable custom analytics instrumentation.

Apple

I joined Apple at the end of 2014 to participate in building the full support for RTL languages. Our effort led to the full support of RTL in UIKit and has shipped in iOS 9. It also got mentioned in WWDC 2015 platform state of the union and the individual session New UIKit Support for International User Interfaces.
You can also watch the WWDC 2016 session What's New in International User Interfaces as a continuation of the same team's effort in iOS 10 and macOS Sierra.

Stanford

Cycleomics is a CareKit and ResearchKit based app that I built for a Stanford research project. The research studies women's health and the data is being collected using the iOS app. The code is open source and you can find the project on my Github and I hope whoever building solutions for health industry.

Vectorworks

During my time at Vectorworks I built several mission critical web platforms including the migration of the main website, the Vectorwork Scholarship portal and the Vectorworks Getting Started Guide portal. Almost all of these are still in production.

Startup Experience

I worked at several Silicon Valley startups and advised a few of them. I did full stack product development and testing and also developed iOS and Watch apps. I also have experience leading a small team of developers.