Senior Software Engineer - Messaging & Agentic AI

We are looking for a Senior Software Engineer - Messaging & Agentic AI to join a product engineering team building the next generation of communication and messaging capabilities for a global SaaS platform.
This is a full-stack role with a strong backend focus. You will work across an existing production platform and newly developed services, helping modernize the messaging architecture and build APIs that support traditional user interfaces, third-party integrations, and emerging AI-agent workflows.
The current messaging solution is part of a large PHP-based legacy monolith. The team is incrementally migrating functionality into independently deployable Node.js and TypeScript microservices. You will need to understand, troubleshoot, and safely modify the existing PHP implementation while helping design and build the new architecture.
The role covers business inbox integrations, custom sender identities, messaging automation, campaign-specific workflows, reliable message delivery at scale, and agent-ready APIs. We are looking for a strong backend engineer who is also comfortable contributing to React and TypeScript user interfaces when needed.

Employment Type: Full-time Employment Contract
Location: Warsaw / Remote


Responsibilities:

• Design, develop, and operate scalable backend services supporting email and messaging capabilities
• Understand and improve existing functionality within a PHP monolith while helping migrate it into Node.js and TypeScript microservices
• Analyze legacy code, dependencies, and data flows to define service boundaries, APIs, data ownership, and safe migration strategies
• Design APIs and agent-facing interfaces that allow messaging capabilities to be safely and reliably used by AI agents, including well-defined actions, structured schemas, permissions, validation, idempotency, and error handling
• Build agents and expose them as services that other agents can discover and call using A2A or similar protocols
• Contribute to agent integration patterns, including REST/GraphQL APIs, tool definitions, and MCP-based interfaces where appropriate, with appropriate security, governance, and observability
• Build secure integrations with Google Workspace, Microsoft 365, and other external communication providers
• Develop capabilities for customer-managed inboxes, domains, sender identities, and messaging automation
• Design APIs, background jobs, queues, and event-driven workflows with reliable handling of retries, rate limits, idempotency, and provider failures
• Improve email authentication, deliverability, bounce and complaint processing, suppression management, and sender reputation
• Contribute to React and TypeScript user interfaces for messaging configuration, automation, and monitoring
• Improve automated testing, observability, performance, and reliability across legacy and new services
• Collaborate with Product, Design, QA, DevOps, Architects, and other engineering teams to deliver high-quality solutions
• Review code, mentor other engineers, and use AI-assisted development tools to improve engineering efficiency and quality.

Requirements:

• 5+ years of professional software development experience, including ownership of complex production systems
• Strong backend development experience with Node.js and TypeScript
• Good working knowledge of PHP, with the ability to understand, debug, and safely modify an existing PHP codebase
• Experience modernizing legacy applications or incrementally migrating functionality from a monolith into microservices or serverless architectures
• Experience designing and building REST or GraphQL APIs, third-party integrations, and asynchronous processing workflows
• Experience designing APIs for machine-to-machine or agent-driven use, with clear contracts, structured schemas, predictable behavior, and strong error handling
• Strong knowledge of relational databases, data modeling, transactions, and query optimization.
• Experience with OAuth 2.0, external provider authentication, secure token management, rate limits, retries, and failure handling
• Experience working with AWS or another major cloud platform
• Experience building customer-facing applications with React and TypeScript
• Strong understanding of automated testing, CI/CD, observability, and production support
• Strong problem-solving and communication skills, with the ability to independently own features from technical discovery through production rollout
• Upper-Intermediate or higher English proficiency, both written and spoken

Nice to have:

• Familiarity with JSON Schema, OpenAPI, function calling, or Model Context Protocol (MCP)
• Experience building AI agents, copilots, LLM-based applications, or workflow orchestration platforms, particularly with frameworks such as LangGraph, CrewAI, or Strands Agents and platforms such as AWS AgentCore
• Experience developing email, messaging, notification, or communication platforms, including automation, sequencing, scheduling, or campaign orchestration
• Experience integrating with Google Workspace, Gmail APIs, Microsoft Graph, or Outlook 365.
• Knowledge of email delivery and authentication technologies, including SMTP, SPF, DKIM, DMARC, and Amazon SES
• Experience with message queues and event-driven technologies such as Kafka, SQS, SNS, or EventBridge.
  
  

What we offer:

• Work on a technically challenging modernization project combining legacy systems, modern TypeScript services, messaging infrastructure, and Agentic AI
• Significant ownership over architecture and production features
• Collaboration with experienced engineers, architects, product managers, QA, DevOps, and design teams
• Flexible remote working model
• 26 days of vacation plus additional holidays
• Medical, life, and business travel insurance
• Stock options
• Home office, internet/mobile, wellness, and professional development support.