Backend Engineer

360 Synergy is a B2B SaaS platform for the US market  - a Gamified HR & Culture Platform. We help service companies retain and motivate their field crews through gamification, HR onboarding, Google review collection, and an AI assistant built into the product.
 

Stack
• Kotlin 2.2, Spring Boot 3.5, JDK 21
• PostgreSQL + pgvector, Flyway
• Spring AI (OpenAI, RAG / vector store, moving toward tool calling)
• WebSocket (in-app messenger: channels, presence, reactions)
• Quartz, Stripe, AWS S3
 

What you'll be doing
• Growing the monolith's domain modules: rewards/points, badges, leaderboard, check-ins, reviews, chat, subscriptions and more.
• Growing the product's AI layer. Today we have RAG search over FAQs and documents plus a few AI helper services (single-shot completion calls to OpenAI). Your job is to grow this into an agentic AI assistant with tool calling: the LLM calls business services as tools, works across multiple turns, and performs actions in the system (create an event, send a reminder, etc.) with user confirmation.
• Integrating the AI assistant into the existing in-app chat module (WebSocket).
• Working with the role-based access model — AI tools must inherit the same permissions as regular API endpoints.
 

What we're looking for
• Production Kotlin (not just the syntax) + Spring Boot / Spring Data JPA
• PostgreSQL: non-trivial queries, hands-on experience with migrations (Flyway/Liquibase)
• REST API design, transactions, Spring Security / JWT
• Required: real experience integrating LLMs into a backend — Spring AI, LangChain4j or direct OpenAI/Anthropic API calls, including function calling / tool calling. Not just "bolting GPT on for text generation".
• Nice to have: pgvector or another vector store, RAG architectures
• Bonus: WebSocket, Stripe API, AWS (S3), Quartz / schedulers

Experience
• 3+ years of commercial development in Kotlin/Java + Spring
• At least one shipped project with an LLM integrated into a production backend (not a pet project) — we'll dig into tool calling and agentic patterns during the interview
• Product team experience (rather than an outsourcing pipeline) is a plus: we need someone who understands the business logic, not just tickets
• English good enough for documentation and day-to-day communication with US stakeholders
 

How you work (important)
We expect you to write code alongside an AI agent (Claude Code, Cursor, etc.) as a primary tool, not just for line autocomplete. This isn't about "AI does the work for you" - it's about speed, and about being able to quickly verify and justify any code you commit, no matter who wrote it. 
 

In your cover letter, briefly tell us which AI coding tool you use and how you typically brief it. Applications without this will not be prioritized.