KAYAK, part of Booking Holdings (NASDAQ: BKNG), is a leading travel search engine. With billions of queries across our platforms, we help people find their perfect flight, stay, rental car and vacation package. We're also transforming business travel with a new corporate travel solution, KAYAK for Business. As an employee of KAYAK, you will be part of a travel company that operates a portfolio of global metasearch brands including momondo, Cheapflights and HotelsCombined, among others. From start-up to industry leader, innovation is in our DNA and every employee has an opportunity to make their mark. Our focus is on building the best travel search engine to make it easier for everyone to experience the world.   KAYAK is seeking a Senior Java Software Engineer to join our Retention and CRM team! The Retention team powers the backend systems behind our Trips product and builds features that keep travelers coming back to KAYAK again and again. The CRM team designs and scales the platform behind personalized email and push notifications delivered to millions of users. In this role, you'll collaborate with engineers, product managers, and marketing specialists to build meaningful, high-impact experiences across both areas. This role is required to work from either our Cambridge or Concord, MA office 3 days per week.   In this role you will: * Design and deliver scalable, high-quality backend services across both Retention and CRM — including systems that power the Trips product, user re-engagement features, and large-scale email and push notification pipelines. * Develop and improve backend services handling bulk and transactional messaging at scale, ensuring reliability and performance across millions of sends. * Build and maintain backend features that drive user retention — including Trips functionality, price alerts, and personalized engagement touchpoints that bring travelers back to KAYAK. * Architect and maintain robust integrations with third-party APIs and marketing platforms, ensuring data integrity and scalability across the email and retention stack. * Lead the design of complex features end-to-end — from technical scoping and architecture decisions through deployment, monitoring, and production support. * Collaborate with cross-functional teams including product managers, marketing specialists, designers, and globally distributed engineers to translate business requirements into well-engineered solutions. * Debug and optimize full-stack solutions, proactively identifying performance bottlenecks, data pipeline failures, and production issues — and driving them to resolution. * Contribute to engineering excellence by upholding coding standards, PR review practices, and operational monitoring, including alerting and incident response for team-owned systems. * Coach and mentor junior and mid-level engineers through code reviews, design discussions, and knowledge sharing, helping to raise the technical bar for the team. * Explore and apply emerging technologies — including AI-assisted tooling and automation — to improve developer productivity, personalization, and platform capabilities.   Please apply if you have: * 5+ years of professional software engineering experience, with a track record of delivering high-quality, production-grade backend systems in a fast-paced environment. * Strong, proven programming skills in Java, with the ability to independently design, implement, and own complex backend features end to end. * Solid experience with APIs and SQL — including designing and consuming RESTful APIs and working with relational databases such as MySQL or similar systems. * Experience leading the design and delivery of complex technical solutions, including making architectural tradeoffs and owning features through deployment and ongoing operations. * Experience collaborating cross-functionally with product managers, marketing partners, designers, and globally distributed engineering teams to ship impactful features. * A collaborative mindset and openness to learning and sharing ideas, including a willingness to mentor others through code reviews and knowledge sharing. * Ability to manage multiple priorities and adapt to changing needs without requiring close direction, balancing sprint commitments with longer-term technical work. * Education in Computer Science or a related field, or equivalent practical experience and transferable skills. * Experience with HTML and CSS is a plus, especially when debugging or collaborating on full-stack solutions with partner teams.   Benefits and Perks * Work from (almost) anywhere for up to 20 days per year * Focus on mental health and well-being: * Company-paid therapy sessions through SpringHealth * Company-paid subscription to HeadSpace * Company-wide week off a year – the whole team fully recharges (and returns without a pile-up of work!) * No meeting Fridays * Paid parental leave * Generous paid vacation + time off for your birthday * Paid volunteer time * Focus on your career growth: * Development Dollars * Leadership development * Access to thousands of on-demand e-learnings * Travel Discounts * Employee Resource Groups * Competitive retirement and health plans * Free lunch 2 days per week * Fun quarterly events such as boat trips, arcades, ski trips, Thursday happy hours, and more   There are a variety of factors that go into determining a salary range, including but not limited to external market benchmark data, geographic location, and years of experience sought/required. The range for this Massachusetts-based role is $140,000 - 160,000.00, not inclusive of annual bonus and recurring RSU grants. We offer a competitive base salary and benefits including: health benefits; flexible spending account; retirement benefits; life insurance; paid time off (including PTO, paid sick leave, medical leave, bereavement leave, floating holidays and paid holidays); and parental leave benefits.     Inclusion At KAYAK, we want everyone to have the space to grow, share ideas and do great work. That's why we're focused on hiring the best talent from all walks of life and experiences, supporting them well and making sure no one feels like they have to fit a mold to belong here. Need any adjustments for the interview, application or on the job? No problem – just give us a heads-up. We've got you.     #LI-EI1