Principal Software Engineer - Backend or Data

Description

Yahoo Mail is the ultimate consumer inbox with hundreds of millions of users. It’s the best way to access your email and stay organized from a computer, phone or tablet. With its beautiful design and lightning fast speed, Yahoo Mail makes reading, organizing, and sending emails easier than ever.

The Mail Intelligence team builds the brains of Yahoo Mail: large-scale intelligent systems that uncover interests, reveal habits, and personalize journeys across the Yahoo ecosystem. Using NLP, GenAI, and ML, we extract insight from billions of messages and turn it into personalized utility for users. This is an AI first, high-standards team where code quality, architectural rigor, and an entrepreneurial mindset are fundamental.

Requirements

• An excellent software engineer first. Strong computer science fundamentals: data structures, algorithms, operating systems, networking. You've built complex systems at scale and are the person others come to when a design is hard.
• Deep in data, capable in serving; or the reverse. You are an expert in one of these and fluent in the other: (a) large-scale data systems: batch and streaming pipelines, SQL, Spark; (b) high-throughput backend services: low-latency, stateful and stateless architectures. You want to work across both.
• Uncompromising on quality. You hold high standards for data integrity and system reliability, and you build systems that prevent failures rather than recover from them manually.
• AI-first. You use AI coding assistants and LLMs as a standard part of how you design, build, and validate software, and you know how to review and harden AI-generated code rather than just accept it.
• Global collaborator. You work well across time zones (Ireland/US), giving clear technical guidance to multidisciplinary teams.
• Your Responsibilities
• Own key features in the Mail Intelligence mission: design, build, and evolve the backend services and data pipelines that power AI/ML personalization and assistive intelligence for 220+ million users.
• Lead performance and scalability work across the stack, balancing cost, quality, and speed as our systems handle billions of transactions.
• Build for resilience: self-healing pipelines, graceful degradation, and automated diagnostics that minimize manual recovery.
• Establish automated frameworks for data quality and compliance across petabyte-scale datasets.
• Act as a technical liaison between Dublin and US-based teams, aligning data and service architecture roadmaps.
• Raise team velocity by setting best practices for AI-assisted development, including the validation, security, and scalability review of AI-generated code.
• Bachelor's degree in Computer Science or a related field.
• 8+ years of professional experience in backend engineering, data engineering, or big data processing, with a significant portion on complex, high-scale systems.
• Deep proficiency in at least one object-oriented language (Java or Python preferred) and strong SQL.
• Hands-on experience building batch or streaming data pipelines (Spark or equivalent), or building high-scale server applications, with working knowledge of the other.
• Experience building and deploying on a public cloud platform.
• Demonstrated use of AI coding assistants (e.g., GitHub Copilot, Cursor) and LLMs (e.g., Claude, Gemini) to increase development throughput and code quality.
• Excellent verbal and written communication, with the ability to influence technical direction across international teams.
• Preferred Qualifications
• Experience in spec driven development.
• Google Cloud Platform, particularly DataProc, Dataflow, Composer/Airflow.
• Hadoop ecosystem experience.
• Prior experience with email protocols, high-volume messaging platforms, NLP, or large-scale personalization engines.
• Experience bridging international engineering hubs.
• 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.
• The compensation for this position ranges from €92,850.00 - €154,750.00 /yr and will vary depending on factors such as your location, skills and experience. Your package may also include incentive compensation opportunities in the form of discretionary annual bonus or commissions. Our benefits include healthcare, pension and a flexible package you can adapt to your own needs.
• Currently work for Yahoo? Please apply on our internal career site.

Conditions

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, serving over 220 million monthly active users. We handle billions of inbound connections a day and trillions of messages on petabyte-scale infrastructure. Our mission is to help users manage the business of their lives through a fast, intelligent, beautifully designed experience.