YugabyteDB is an open-source distributed relational database designed to handle large-scale data in various environments. It offers strong consistency, high availability, and scalability, making it suitable for mission-critical applications. Unlike traditional monolithic databases, YugabyteDB's distributed architecture allows for horizontal scaling, which can lead to single-digit ms latency. The system provides automatic load balancing for YCQL, a NoSQL API, but recommends external load balancers for YSQL, a fully relational API. Sizing the cluster requires considering read/write transactions per second and running workload generators to determine optimal cluster size. YugabyteDB supports multiple APIs, including YSQL and YCQL, which cater to both relational and NoSQL workloads. The system also offers row-level geo-partitioning for managing data residency across regions.