We are looking for a Senior .NET C# Developer to join a growing European Platform & APIs team. This is a strategic senior-level role with direct impact on architecture and platform evolution. You’ll be instrumental in implementing our new strategic architecture, transitioning from our current mix of monolith and microservices toward an increasingly event-driven, service-oriented architecture. Additionally, you will need to have experience with Windows form development as we require support delivering incremental changes to existing desktop applications.Project — the client’s platform and APIs manage significant complexity: a real-time processing pipeline handling complex documents with distinct data models, alongside the intricate structures and contracts between client’s microservices. This is a distributed, high-load environment with strict latency requirements and complex microservice contracts.Requirements:5+ years of professional experience with .NET / C#2+ years developing desktop applications using Windows FormsStrong microservices architecture expertise, particularly event-driven patternsProduction experience with AWS (SQS, S3, EC2 or similar)Experience with SQL and NoSQL databases (MongoDB & Elasticsearch preferred)API design and development experienceSolid knowledge of async/await, threading, and resource managementExperience working with distributed systems: Message queues (SQS, RabbitMQ, Kafka, etc.), Retry strategies, IdempotencyLogging & debugging in distributed environmentsTrack record of refactoring and modernizing legacy systems while maintaining reliabilityStrong analytical and architectural thinkingPerformance-focused mindsetQA-driven thinking (edge cases, failure modes, resilience)Advanced English and betterNice to Have:Experience with high-volume web scraping or document processing systemsExperience in financial services or real-time data processing environmentsKnowledge of ElasticsearchPython experience for data workflowsDocker / Kubernetes experienceUnderstanding of financial services or real-time data processing requirementsResponsibilities:Migrating and refactoring core platform components to modern architectures (initial focus, ~100% of time)Modernizing infrastructure by migrating services to the latest versions of MongoDB, Elasticsearch, and .NET (currently 4.7.2, moving to latest)Building greenfield APIs that expose platform capabilities to our next-generation web applications (growing to ~80% of time as migration stabilizes)Supporting web app teams through collaborative API design, documentation, and troubleshootingImproving platform reliability by increasing test coverage, velocity, and effectivenessWe offer:Vacation (up to 20 working days)Sick leaves (10 working days)National Holidays as time off (11 days)Medical Insurance after 3 months probation period (can be used in Ukraine)Online English coursesAccountant assistance and legal supportFlexible working schedule, remote, office-based or hybrid formatFully-equipped perfect office space located in the city center (ready for work in blackouts)Direct cooperation with the customerDynamic environment with low level of bureaucracy and great team spiritCommunication with Top/Senior level specialists to strengthen your hard skillsOnline/offline teambuildingsVolunteering culture development and supportВідгукнутись на вакансію