Principal Backend Engineer (IC5)
Please Note: To support collaboration in this newly established team, the role requires on-site attendance at our Dublin office two days per week.
Applicants must have the legal right to work in Ireland at the time of application.
A little about Us
Yahoo Mail is the ultimate consumer inbox for over 220 million monthly active users. We manage billions of daily connections and trillions of messages across a massive, petabyte-scale infrastructure. Our mission is to help users run "the business of their life" through a fast, intelligent, and beautifully designed organized experience. We are currently executing a 100% native public cloud transformation, presenting a once-in-a-career opportunity to re-architect global-scale systems.
About the Team
The Mail Intelligence Org develops the "brains" of Yahoo Mail. We build large-scale intelligent systems that uncover user interests, reveal habits, and personalize journeys across the Yahoo ecosystem. Using NLP, GenAI, and advanced ML, we extract insights from billions of messages to create enhanced content and personalized utility. This is a high-impact team where code quality, architectural rigor, and an entrepreneurial mindset are fundamental.
A lot about YOU
Who YOU Are
Architectural Mindset: You are a "go-to" technical expert in building complex, stateful/stateless systems at massive scale.
Attention to Detail: You maintain high standards for system quality and are committed to delivering robust, scalable solutions that serve 200+ million users.
AI-Forward Practitioner: You view AI as a force-multiplier, with a proven ability to integrate AI coding assistants and LLMs into your daily development, documentation, and system-design workflows.
Core skills depth: You have a strong understanding of computer science fundamentals, including Data Structures, Algorithms, OS, and Networking.
Problem-Solving Depth: You possess advanced analytical skills, capable of solving multifaceted backend challenges using both traditional computer science fundamentals and modern AI-driven approaches.
Collaborative & Global: You excel in distributed environments, effectively coordinating with teams across time zones (USA/Ireland) to maintain architectural alignment.
Responsibilities:
The Mission: Own key features in the Mail Intelligence mission - make the Yahoo! Mail inbox the go-to app for managing the business of life.
System design: Lead the design and build of robust, high-throughput backend architectures and services that power personalization and assistive intelligence for hundreds of millions of users.
AI-Augmented Engineering Leadership:
Drive organizational velocity by establishing best practices for AI-assisted development to optimize complex codebases and accelerate cloud-native migrations
Proactively identify and automate repetitive backend tasks or diagnostic processes using AI-driven agents and internal tools to improve team operational health.
Oversight & Validation: Act as a primary reviewer and architect, moving beyond manual execution to focus on the validation, security, and scalability of AI-generated code and automated workflows.
Performance & Scalability Ownership: Drive continuous optimization of system performance, ensuring our infrastructure handles billions of transactions with maximum efficiency and minimal latency.
Technical Strategy & Influence: Partner with tech leads and architects to align complex backend strategies with global business objectives, balancing quality, cost, and speed.
Resiliency Engineering: Lead the implementation of sophisticated feedback and recovery mechanisms to ensure system "graceful degradation" and 24/7 reliability.
Qualifications
Educational Requirement: Bachelor's degree in Computer Science or a related field.
Experience: 8+ years of professional experience in backend engineering, with a significant portion dedicated to complex, high-scale server applications.
Technical Mastery: Deep proficiency in Java, C++, or similar OOP languages. Expert-level understanding of Data Structures, Algorithms, OS, and Networking.
Cloud Expertise: Extensive experience building and deploying on public cloud platforms (Google Cloud Platform is a plus).
AI Fluency: Demonstrated experience leveraging AI coding assistants (GitHub Copilot, Cursor, etc.) and LLMs (Gemini, Claude) to increase development throughput and code quality.
Proven Impact: Experience leading the architecture of systems that impact significant user-facing objectives or organizational strategies.
Preferred Qualifications
Educational Requirement: Master’s degree in Computer Science or a related field (with a focus on computational systems).
Mail & Intelligence: Prior experience with email protocols, NLP, or building large-scale personalization engines.
AI Experimentation: A documented commitment to staying current with emerging AI tools and a proactive mindset toward experimenting with new automation workflows.
Global Collaboration: Experience working as a bridge between international engineering hubs.
Yahoo is proud to be an equal opportunity workplace. All qualified applicants will receive consideration for employment without regard to, and will not be discriminated against based on age, race, gender, color, religion, national origin, sexual orientation, gender identity, veteran status, disability or any other protected category. Yahoo will consider for employment qualified applicants with criminal histories in a manner consistent with applicable law. Yahoo is dedicated to providing an accessible environment for all candidates during the application process and for employees during their employment. If you need accessibility assistance and/or a reasonable accommodation due to a disability, please submit a request via the Accommodation Request Form (www.yahooinc.com/careers/contact-us.html) or call +1.866.772.3182. Requests and calls received for non-disability related issues, such as following up on an application, will not receive a response.
Yahoo has a high degree of flexibility around employee location and hybrid working. In fact, our flexible-hybrid approach to work is one of the things our employees rave about. Most roles don’t require specific regular patterns of in-person office attendance. If you join Yahoo, you may be asked to attend (or travel to attend) on-site work sessions, team-building, or other in-person events. When these occur, you’ll be given notice to make arrangements.
If you’re curious about how this factors into this role, please discuss with the recruiter.
Currently work for Yahoo? Please apply on our internal career site.
