Back end Engineer [Brazil]

About Arena: Arena is a Series A company backed by top-tier investors such as CRV, Redpoint and Craft Ventures. Arena offers a unique work environment and the chance to collaborate with diverse teammates across multiple countries, with a culture of ownership (autonomy, growth, and responsibility). We are a startup created in Silicon Valley with a mission to build communities for creators, publishers and brands with the power of AI. Companies using Arena include Disney, Reuters, Fox, Red Bull and NFL. We have +2,000 customers in 150 countries and with +50M users having conversations on Arena per month and engaging with our Agent AI. Sometimes you're stuck in a job that doesn't make sense. Refactoring code from ages ago, the stack is miles away from what it's supposed to be. If you love a good challenge, enjoy solving meaningful problems, and want to be a part of one of the fastest-growing AI startups in the Silicon Valley — then Arena is the company you're looking for. What you will be doing: Our team is made up of very experienced engineers, some with more than 10 years of experience. You will have an enormous impact on making our app and API service faster, more scalable and more flexible. You will collaborate with product and engineering teams to ship AI-powered features and make the existing ones perform orders of magnitude faster. The challenges: Real-time messaging to support 500,000 concurrent users per customer application; High performance: our API responses are in the 10ms range; Design and build AI Agents, RAG pipelines, model fine-tuning and crawling. High scalability: we use sharding, master-master, and master-slave to ensure scalability; High availability: our code is running on homepages of the most visited websites and apps on the internet; Distributed databases for our Data Platform storing every user engagement. Our Stack: Node.js, TypeScript; Golang; Websocket; Apollo GraphQL; AWS Lambda/Serverless framework; AWS (API Gateway, S3, VPC, IAM, Fargate, EC2, ALB, CloudFront, Kinesis, SQS, CloudWatch); Google Firestore/Firebase; MongoDB, PostgreSQL, DynamoDB; Redis; Cloudflare; Unit test. Work Experience: 3+ years as a backend developer Experience with high-traffic and high-performance applications Curious developer who experiments with AI and AI agents everyday. Must-Have Experience: TypeScript; Node.js; TDD, BDD, or ATDD; REST APIs; MongoDB, AWS DocumentDB, or other document database; Nice-to-Have Experience: Experience with statically typed languages (e.g. Java, C#, Go); Object-oriented and functional programming; Golang; AWS; SQL; React. Example Projects You’ll Be Working on: Build a real-time chat that can scale to 1M simultaneous users; Design, optimize and scale AI agent-based architectures, RAG pipelines, and other LLM-driven systems. Integrate systems with data sources and handle millions of first-party data. Build complex business rules orchestrations similar to Reddit, Discord, and Whatsapp. We also have some sweet perks like: 🔥 Be a part of the team in Silicon Valley and join a global team 💪 A team of exceptional engineers leading the cutting-edge AI Agents. 💶 Competitive salary package & benefits ⛱️ 4 weeks of paid time-off 📖 Learning and Development budget 🚀 Key moment to join Arena in terms of growth and opportunities 💻 Ability to put your stamp on real-world AI applications that serve millions of users. 📚 Fast-learning environment, entrepreneurial and strong team spirit 🌍 Multiple nationalities: cosmopolite & multi-cultural mindset 💆‍♀️ Our people matter, work-life balance is important at Arena