MongoDB has made significant progress in addressing its durability and performance issues over the years, but it still falls short in the context of high-performance applications that require low latency and high throughput. The introduction of single-shard transactions in MongoDB 4.0 is a welcome change, but it comes with hidden costs such as lack of horizontal scalability, high latency due to the need for caching, and low throughput due to the primary node handling all write requests. In contrast, modern transactional databases like YugabyteDB deliver transactional guarantees, high performance, and linear scalability, making them a more suitable choice for fast-growing online services.