Backend Engineer

About the role 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.
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
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
🏃 Strava yearly subscription
🏠 Hybrid working style, flexible hours
✈️ Annual company trip + monthly team parties
💻 MacBook provided
📜 Social insurance per Labor Law
Work Location
HCM: 2nd Floor XL Building, 167 Tran Nao, An Khanh Ward
Da Nang: 2nd Floor, 458 Nguyen Huu Tho, Cam Le Ward