Nubank faced significant challenges with its logging system as the company expanded. Initially relying on a third-party vendor for log ingestion and storage, the setup became costly and limited their visibility into log management. As the volume of logs surged, so did expenses, making it difficult for the engineering team to troubleshoot issues. Critical tools tied to the vendor's platform added to the complexity, and spikes in log ingestion slowed down querying processes. To regain control and manage costs, Nubank decided to build an in-house logging platform, breaking the project into two phases. The first phase, called the Observability Stream, focused on reliably ingesting and processing logs from thousands of applications. They selected Fluent Bit as the log forwarder and developed in-house services to buffer and filter logs before storage. This setup improved reliability and allowed for better management during traffic spikes. The second phase involved creating a Query and Storage Platform that made logs easy to search and analyze. This two-phase approach not only facilitated smoother migration but also enabled testing and refinement of each component. Nubank aimed for a solution that was reliable, scalable, and cost-effective, ultimately ensuring that their logging system could evolve alongside the company’s growth.