Top 3 reasons to join us

• Competitive salary packages.
• Dynamic and open-sharing working environment.
• Hybrid and flexible working mode.

Job description

Build like a founder. Ship like Spartan.

Our clients are startups in a race: an MVP in 30 days, one demo away from a funding round. We’re looking for a Backend Engineer to run that race with us.

We don’t act like vendors. We embed. Our teams sit inside startups backed by YC, Pear VC, BlingCap, a16z, and Techstars, working beside founders and engineers from Stanford, MIT, Yale, Google, Amazon, and Uber. Together we ship those MVPs and scale the systems behind them to millions of users and billions of requests.

This isn’t outsourcing where you sit three layers away from the client. You’ll be in the founder’s Slack. Your code runs their production. When their demo lands a funding round, that’s your work on the screen.

70% of our portfolio is LLM-powered. Cursor, Claude, and Codex are default tools here, not experiments. You’ll use AI every day, and you’ll be expected to use it well.

Who Thrives at Spartan

Not every environment fits everyone, so here’s an honest picture of the teammate we’re looking for.

You’ll thrive here if:

• You do whatever it takes to win. Multiple hats, unglamorous work included.
• You take on the hardest part of the project and see it through to shipped.
• You pick up a new stack in days, not months, because the project needs it.
• You’d rather own a problem than a ticket.
• Some weeks will stretch you. That’s the job. But you’ll never carry it alone. A critical client release or a tricky production issue? Someone always has your back. We push each other hard because we care how far each of us can go. We win together. We lose together. Nobody gets left behind.
• One last thing. We’re not filling seats. We’re looking for teammates for the battles ahead. If you read all this and something in you said yes, trust that feeling and apply. We respect people who back themselves. Every Spartan here started with that same yes.

What You’ll Do

• Design and build scalable microservices that power high-growth startups.
• Build LLM features end to end: RAG pipelines, vector search, agent workflows, evals.
• Keep AI running well in production: latency, token cost, guardrails, monitoring.
• Ship fast with a proven process: async standups, PRDs/RFCs, code reviews, and an AI-native workflow on Cursor, Claude, and Codex.
• Keep the bar high: clean code, testing, documentation, reliability.
• Talk directly with US startup founders and product leaders. Your input shapes their product.
• Wear more than one hat. Backend first, but you’ll touch infra, data, and AI integration when the project needs it.
• Help shape Spartan’s engineering culture. We work like founders, not contractors.

Your skills and experience

What We’re Looking For

• Fluent English. You’ll talk directly with US startup founders.
• 2+ years of solid backend experience in any language. We mostly run Java, Kotlin, and TypeScript, but strong fundamentals and fast adaptation beat any specific stack.
• Strong CS fundamentals: algorithms, data structures, scalability.
• Experience with testing, dependency injection, and distributed systems.
• You use AI tools like a pro: you review what they write, catch their mistakes, and know when not to use them.
• A builder’s mindset. You don’t just code, you solve problems like an owner.

Nice to Have

• You’ve shipped an LLM feature to production: RAG, agents, or direct model integration.
• You’ve built with agent tooling: MCP servers, LangGraph, or the Claude Agent SDK.
• You’ve run evals on an AI feature: Ragas, Promptfoo, LangSmith, or your own harness.
• Hands-on with vector databases: pgvector, Pinecone, Qdrant, Weaviate.
• Experience with Kafka or other event streaming systems.

Tech We Use

Every project brings a different stack, so in a year here you’ll touch more of this list than most engineers do in five. What we adopt is decided by our engineers through an internal Tech Radar, not handed down from a slide deck.

Languages: Go · Java/Kotlin/Scala · TypeScript · Python

Data: Postgres · MongoDB · DynamoDB · ElasticSearch · Redis

LLM stack: Claude API · OpenAI API · MCP · LangGraph · LangSmith

Vector search: pgvector · Pinecone · Qdrant · Weaviate

Streaming: Kafka · Pulsar · SQS · AWS Kinesis · GCP Cloud Tasks

Data processing: Spark · Flink

Cloud: AWS · GCP · Azure · Kubernetes

CI/CD: Jenkins · GitHub Actions

Observability: DataDog · Prometheus · Grafana · ELK Stack

AI tooling: Cursor · Claude · Codex

Why you'll love working here

Career Growth

• Work directly with founders from YC, Stanford, MIT, Yale, Google, Amazon, Uber, and more.
• Exposure to LLMs, AI agents, cloud infra, and real-time systems.
• Transparent career path and mentorship from engineers who’ve taken 3 companies to IPO.
• Every project feels like its own mini-startup.

Why Spartan

• 50+ MVPs launched, 3 IPOs, $100M+ raised by the startups we build with.
• 95% engineer retention. People stay because the work is worth staying for.
• You build zero to one. Blank repo to live product in weeks. Most engineers get that chance once in a career. Here it’s the job.
• Your work is visible. What you ship this month is in a founder’s investor demo next month.
• No layers, no bureaucracy. You talk to the decision-maker directly, and decisions land in hours, not weeks.
• Every project is a new market, a new stack, a new problem. One year here teaches what three years elsewhere would.
• You’ll never just take tickets. You’ll own problems, ship fast, and grow with the founders we partner with.

Benefits & Perks

💰 Competitive salary, 100% salary during probation

🏝 Unlimited PTO + public holidays

🩺 Premium healthcare insurance + annual health check

⚽ Sports clubs for every taste: football, badminton, billiards, pickleball

🎮 PS5 and Nintendo at the office

🏠 Hybrid working style, flexible hours

✈️ Company trip + monthly birthday parties

💻 MacBook provided

📜 Social insurance per Labor Law