MongoDB is a popular NoSQL database known for its flexibility and ease of use, but it has limitations in scaling, cost, and operational complexity that can make it less suitable for high-performance, large-scale environments. Companies like SnapDeal and ZoneTap encountered performance issues, high costs, and service interruptions due to MongoDB's scalability issues, sharding complexities, and reliance on primary-secondary replica set model. In contrast, alternative database solutions such as Aerospike offered improved performance, efficiency, and architectural resilience at a lower cost. The experiences of companies in the AdTech industry highlight important lessons for enterprises evaluating their database options, emphasizing the need to consider long-term data needs, scalability, low latency, high availability, and predictable costs when making an informed decision about database technology.