Managing a fintech that earned more than R$9.6 million in just 30 days brings a series of complex challenges. For those on the technical side, especially as senior developers, each day is marked by decisions that can profoundly impact the company. When we are working with a stack composed of NestJS, Redis, PostgreSQL and NextJS, the focus is always on ensuring that the system is scalable, performant and secure, but the reality goes far beyond choosing good tools.

1. The Constant Pressure of Not Being Able to Make a Mistake

In an environment where millions of reais are moved, the margin for error is practically non-existent. Every small technical decision, whether in architecture or in the implementation of a new functionality, can directly affect the business and, consequently, customers and partners. The pressure to ensure all transactions are processed correctly, without fail, is constant. A simple error, such as a poorly optimized query or incorrect cache configuration, can mean considerable losses.

NestJS, being modular and efficient, helps with code organization, but the pressure of keeping everything running flawlessly leads to an extremely careful approach to each new deployment. Each line of code undergoes rigorous reviews and automated testing before being applied, ensuring there is no impact on transactions.

2. Continuous Monitoring and Maintenance

Real-time monitoring is another crucial factor in ensuring fintech operates efficiently. Tools like Sentry for error capture and Grafana for performance metrics are essential in everyday life. They allow us to have a detailed view of how the system is behaving and detect potential failures before they cause a bigger problem.

The use of Redis for processing queues and caching is strategic to handle the high volume of transactions. It helps ease the load on the database and distributes event processing efficiently, but the technical team needs to be constantly vigilant to ensure that no transaction queues get stuck, as this can directly affect the users' experience and cause long delays. .

3. Scalability and Data Consistency

Maintaining the scalability of a system that processes millions of reais requires a well-planned architecture. PostgreSQL, the database we use, requires continuous optimizations such as table partitioning and well-defined indexes, to handle the growing volume of data without compromising the performance. Each query needs to be optimized, and backup routines are constant to avoid any data loss.

The combination of NestJS and PostgreSQL allows the backend structure to be scalable, but ensuring data consistency in complex financial transactions is a constant challenge. We need to deal with competitive scenarios and distributed transactions, which makes development even more challenging.

4. Frontend Development with NextJS

The frontend, developed with NextJS, needs to be fast and intuitive, providing real-time dashboards that show critical financial data for customers. User experience is key, and the use of SSR (server-side rendering) in NextJS helps ensure a fast interface, even with a high volume of data being exchanged between the frontend and backend.

5. Decision Making Under Pressure

In the fintech environment, making quick decisions is part of everyday life. When a problem is detected, there is no time for much deliberation. Action must be taken immediately to mitigate the damage. A simple downtime of minutes can have a direct impact on customers' finances and undermine trust in the platform. Therefore, we have strict protocols to deal with failures, including rollback of deployments and immediate recovery procedures.

Having alerts configured to monitor API performance and possible bottlenecks is essential. If an endpoint starts to have problems, we receive instant notifications and often have to resolve the issue in a matter of minutes, or even seconds.

6. Maintain Balance: Productivity and Quality of Life

Dealing with large financial volumes and the constant pressure to keep the platform operating efficiently can be exhausting. However, it is essential to maintain a balance between productivity and quality of life to avoid excessive team burnout. Collaboration between teams is fundamental, and we seek to have a culture of mutual support, where difficulties are shared and resolved together.

Conclusion

Managing a fintech with significant revenue like ours requires not only advanced technical skills, but also a strong ability to deal with pressure and make decisions quickly. The stack composed of NestJS, Redis, PostgreSQL and NextJS allows us to create a solid and scalable architecture, but the responsibility of maintaining everything Running flawlessly is a constant challenge. In the end, the reward is knowing that we are building a reliable platform that makes the financial lives of thousands of users easier, while continuing to grow and innovate.