Senior Application Platform Engineer w Polska

• Seven or more years building and operating production software, including time in a startup or a small product team where you owned delivery end to end.
• SDK or platform experience: you have designed and shipped a library, SDK, platform service or internal developer platform that other developers consumed, and you lived with the consequences of your API decisions.
• Full stack delivery: modern frontend plus backend services and data stores.
• Cloud in production: AWS preferred, serverless and container workloads, infrastructure as code, CI and CD.
• Identity and multi tenancy: OIDC, session context propagation, tenant isolation and row level scoping.
• FinOps in practice: you have run cost control on a live cloud or AI workload with budgets, quotas, alarms and cost reporting.
• Security as part of the job: secrets handling, untrusted input and untrusted generated code, the common web attack surface.
• Agentic AI across the SDLC: you use coding agents daily to build, test, review and document, you build AI into the products you ship, and you can explain clearly where agents failed you.
• MCP servers and tools, managed LLM services, LLM application patterns such as prompt design, model selection by cost, sandboxing generated code and evaluating AI output quality.
• Integration platform background, iPaaS, Salesforce, SAP, Jira or Grafana.
• Hands on work inside a SOC 2 or ISO 27001 scope.
• English at working level for a distributed team.

Matrix Eastern Europe, the offshore division of Matrix IT, one of the leading global R&D services companies with more than 11,000 professionals, is looking for a Senior Application Platform Engineer to join one of our teams!

Our client builds an enterprise application platform where business users run governed applications from a single workspace. We are forming a small product engineering team that builds the SDK behind that platform and the applications that run on it.

As the senior engineer you own the SDK: the client library that application developers use and the platform side contracts behind it. You also set the engineering bar for every application the team ships. The team is deliberately small, so you build as well design.

,[Own the SDK end to end: client library surface, platform side services, packaging, documentation and a reference application., Make the SDK real by building applications on it. Every application the team ships is both a product and the proof that the SDK works., Build governed applications: environment connectivity, single sign on, identity context passed through to the data layer, health and monitoring, metered AI with budgets and usage reporting., Deliver the full range of application types: AI native data applications, operational tools such as task and workflow management, and integrated dashboards over systems like Jira, Grafana and Salesforce., Own production: deployment pipelines, version stamping, post deploy smoke tests, automatic rollback, alarms and cost controls., Set and enforce the engineering standard, review code and mentor the second engineer on the team.] Requirements: https://jobeax.com/link/JSd7UYCSg572jJDY, React, SDK, AWS Lambda, AWS, Kubernetes, Terraform