Back end Engineer [Brazil]

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.

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 Silicon Valley — then Arena is the company you're looking for.

What you will be doing:

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 improve existing ones.

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.

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).