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 th