Principal Application Engineer

Application Modernization Platform (“AMP”) is a MongoDB offering that modernises our customer’s legacy relational applications to a modern architecture underpinned by MongoDB using a combination of software, processes, and engineers. In this offering, the people and software are inextricably linked and cannot be separated. The delivery happens in an accelerated timeframe wherein the team takes advantage of GenAI and algorithmic tooling to expedite the turnaround time for application delivery. AMP team generally works with enterprise-grade customers, in all verticals on a variety of exciting use cases. This role solves technically sophisticated problems, gains incredible cross-stack experience, works with top-notch people in the business, addresses multiple customer-facing opportunities. The role also becomes the forefront of groundbreaking R&D that enables further acceleration for enterprises working across a variety of technologies. AMP exists to expedite time to value for customers who are looking forward to changing, modernising and updating their tech stack while keeping MongoDB the cornerstone of their system architecture. Work as a software developer in an Agile environment delivering solutions for customers focused on migrating our customers’ legacy relational-based Java applications to a more modern cloud-based architecture running on MongoDB, leveraging the latest GenAI tools and approaches to accelerate this process. During each project, successful candidates will be required to innovate on potential new GenAI-based solutions for specific challenges in addition to applying existing playbooks and tooling for migration. This role will be based remotely in France. Position Expectations • Shape architecture and technology strategy across AMP modernization projects and workstreams, making complex technical decisions with limited supervision and connecting engineering choices to customer and business outcomes • Lead the assessment and modernization of legacy Java applications by uncovering dependencies, embedded business logic, integration points, and operational constraints; recommend fit-for-purpose modernization paths rather than defaulting to lift-and-shift • Design, implement, and review production-quality solutions using Java and Spring Boot, including APIs, integrations, monolith decomposition, relational-to-document data modeling, stored-procedure transformation, schema evolution, and MongoDB operational practices • Establish safe, incremental delivery practices through explicit acceptance criteria, automated testing, CI/CD, observability, and rollback, dual-run, or other risk-control strategies; identify quality, security, performance, and reliability risks and guide teams to resolve them • Serve as a senior technical partner to customers, application owners, and account and project stakeholders by explaining complex topics clearly, aligning priorities, navigating disagreement, communicating trade-offs, and maintaining trust through high-risk change • Multiply the effectiveness of engineers by mentoring, raising engineering standards, creating reusable migration playbooks and documentation, applying GenAI advancements responsibly where valuable, and influencing project direction without relying on formal authority Requirements • Professional fluency in French is required • Bachelor’s degree in Computer Science, Information Technology, or a related field, or equivalent practical experience • Typically 8+ years of progressive experience designing, building, and delivering Java applications, including significant experience leading complex application modernization initiatives • Expert understanding of Java fundamentals, object-oriented design, concurrency, error handling, performance considerations, and maintainable software architecture; able to review code and guide design decisions across teams • Deep production experience with Spring Boot and related patterns for building resilient services, APIs, integrations, and testable distributed applications • Demonstrated ability to assess legacy estates, decompose monoliths, uncover dependencies and embedded business logic, and define practical modernization strategies with clear trade-offs • Strong experience with relational databases and SQL, including stored procedures, data dependencies, data migration, schema evolution, and relational-to-document modeling for MongoDB or comparable document databases • Proven history of delivering high-cadence modern applications using Agile methodologies, test-first development, CI/CD pipelines, Git-based version control, observability, and reliability practices; demonstrated success mentoring engineers and influencing technical outcomes across teams Nice-to-have skills • Experience in building REST APIs with Spring Boot • Experience in performance and memory optimization of JAVA applications • Familiarity with tools like Postman, IntelliJ IDEA, and Maven/Gradle • Exposure to other languages or technologies like JavaScript, .Net • Understanding of ORM tools like Hibernate, Spring Data or JPA (even through coursework or self-study) • Experience in nascent GenAI technologies and approaches, such as using OpenAI/Anthropic API not purely through chat interfaces • Experience with AI-powered development tools like Claude Code, Cursor, or similar code assistants • Good experience of using MongoDB Successful candidates will engage with customer systems and may be exposed to highly confidential customer data, including but not limited to non-public information. For this reason, and due to the nature of the highly regulated industry in which our customers operate, successful candidates may be subject to enhanced background checks, security screenings, and possible constraints around the trading of securities. Successful candidates will understand these requirements and be willing to participate in enhanced screenings and constraints as required by MongoDB and its customer