Senior iOS Engineer developing Thunderbird’s privacy-focused mobile email application. Improving architecture, performance, security, and reliability for millions of open-source users.
Responsibilities
Build and refine Thunderbird’s mobile products and platform architecture
Improve scalability, performance, reliability, and user experience
Develop a deep understanding of the codebase and architecture to make changes across the entire stack
Maintain debugging and testing practices across unit, integration, and automated testing
Review code and guide improvements to architecture, testing, and development best practices
Resolve complex issues involving performance, security, and cross-platform integration
Monitor application health and address issues before they escalate
Document technical decisions, system architecture, and team processes
Own assigned projects from investigation and planning through development, validation, and delivery
Collaborate cross-functionally with mobile engineers, product management, UX, open-source contributors, and the broader Mozilla ecosystem
Ensure mobile development meets accessibility, security, and privacy standards
Requirements
7+ years of professional software development experience, including 2+ years in a Senior Software Engineer role
3+ years of professional mobile application development experience
Strong experience with Swift, SwiftUI, and iOS frameworks
Deep knowledge of iOS architecture, design patterns, and performance optimization
Experience delivering and maintaining complex, scalable, and reliable software
Experience addressing technical debt and refactoring large or complex codebases
Strong knowledge of mobile security, including encryption, secure storage, app signing, and vulnerability remediation
Experience with communication and email protocols such as RSS, IMAP, POP, or Matrix
Familiarity with IETF standards for CalDav or CardDav
Advanced proficiency with Git and collaborative development workflows
Strong debugging, testing, and problem-solving skills
Ability to work independently, take ownership, and collaborate across teams
Excellent async written communication skills; comfortable working with a geographically distributed team
Ability to learn, evaluate, and responsibly use emerging technologies, including AI-enabled tools
Applicants must reside in the United States and have permanent work authorization; visa sponsorship is not provided
Bonus: Familiarity with Apple App Store and Google Play Store compliance guidelines
Bonus: Experience contributing to open-source projects or communities
Bonus: Proficiency in French, German, Japanese, or another widely supported Thunderbird language
Benefits
Fully remote work & schedule flexibility
Company-provided laptop
Annual bonus program
Monthly remote work stipend
Annual professional development stipend
Access to Coursera learning platform
Industry conferences
Company all-hands and team gatherings
24 days PTO per year (prorated)
Your birthday
Year-end company shutdown
9 wellbeing days
Public holidays
Other paid leave
Quarterly wellbeing stipend for personal / family activities
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