Senior Mobile Engineer

Who you are

• 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, and familiarity with the IETF standards for CalDav or CardDav
• Advanced proficiency with Git and collaborative development workflows
• Strong debugging, testing, and problem-solving skills
• Strong attention to detail, curiosity, and a product-focused mindset
• The ability to work independently, take ownership, and collaborate across teams
• Respect for diverse skills, experiences, and perspectives
• 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, to improve work processes
• Familiarity with Apple App Store and Google Play Store compliance guidelines
• Experience contributing to open-source projects or communities
• Proficiency in French, German, Japanese, or another widely supported Thunderbird language
• You’ll be successful in this role if you look beyond shipping features and improve the architecture, reliability, security, and long-term health of the product. You’re comfortable solving ambiguous problems, flagging risks early, documenting decisions, and collaborating across engineering, product, UX, users, and the open-source community
• We may consider candidates with strong skills but less than the required experience. Title, level and compensation will be determined based on qualifications and experience

What the job involves

• The Senior Software Engineer, iOS is an experienced individual contributor who brings deep iOS expertise to the design, development, and evolution of Thunderbird’s iOS application. This role will continue to contribute to Thunderbirds effort to develop the iOS app and establish a strong technical foundation for the product
• You’ll work closely with mobile engineers, product management, UX, and other partners to deliver a high-quality iOS experience that meets high standards for performance, reliability, accessibility, security, and maintainability
• You’ll play an important role in delivering exceptional user experiences for Thunderbird’s global user base by translating product needs into thoughtful technical solutions and ensuring your work aligns with MZLA’s mission and the objectives of the Thunderbird Project. You’ll also collaborate with open-source contributors and mobile engineers across the broader Mozilla ecosystem
• 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 confidently make changes across the entire stack
• Maintain strong debugging and testing practices across unit, integration, and automated testing
• Review code and guide improvements to architecture, testing, and development best practices
• Independently 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, collaborating cross-functionally, from investigation and planning through development, validation, and delivery
• Ensure mobile development meets accessibility, security, and privacy standards
• Over time, your work will help Thunderbird’s iOS experience become more resilient, scalable, and easier for both staff and community contributors to build on

The application process

• We carefully review every cover letter and screening question, so take the time to answer each fully. We value authentic, thoughtful responses that reflect your own experience and perspective. It is fine to use AI tools to polish your writing, but your answers should be your own. Candidates who submit generic or unoriginal AI-generated responses may be disqualified from further consideration

Benefits

• Health and wellness: Mozilla covers medical, dental and vision plan premiums at 100% for U.S. and Canadian employees. Our offerings give you the options you need to manage your health — and your family’s — the way you want.
• Mental health: Mental health is as important as our physical health. That’s why Mozilla’s health benefits include therapy and coaching sessions to make sure our people have access to the care they need.
• Time away: With all of life’s demands, time away from work to disconnect and recharge is essential. In addition to country-specific holidays (12 in the U.S. and Canada), vacation and sick time start accruing right away (specifics vary by country). Everyone also takes a pause together on quarterly all-company wellness days, plus you get to celebrate the most personal holiday of all: your birthday.
• Parental leave: While Mozilla’s parental leave policies vary globally, our U.S. and Canadian-based employees can look forward to 26 weeks of paid leave for childbearing parents and 12 weeks of paid leave for non-childbearing parents.
• Financial: Mozilla is a private company, so our compensation isn’t tied to stock options or equity plans. Instead, we offer generous, performance-based bonus plans to all regular employees to underscore that we share in our success as one team. As for retirement savings for US and Canadian employees, Mozilla contributes a percentage of your eligible base salary each year to the 401(k) Plan/RRSP (regardless of whether you contribute or not), with 100% vesting.
• Learning and development: We’re big believers in learning by doing, and we also want to invest in your education and development beyond your role. Every employee is eligible for an annual professional development budget. Mozillians can put it toward technical or management training, certifications, conferences and more.
• Help when you need it: Life is full of surprises; that’s why it’s important to be prepared. Mozilla provides Life/AD&D and Short and Long Term Disability insurance (offerings may vary by locale) to ensure that you and your family will have a safety net in place should you ever need it.
• Plus a bit more: A few other benefits include a quarterly wellbeing stipend (to use on those things just for you), an employee referral bonus, internet reimbursement if you’re remote, and a budget for office essentials to make working remotely ergonomically comfortable.