Every database on the planet is a time-series database`, MongoDB suggests, implying that any database capable of storing integers and values can be used for time-series data. The author argues that specialized time-series databases are unnecessary, citing examples such as CSV files, SQL Server, and Oracle. To make informed decisions about time-series databases, it's essential to consider the credibility of the source and conduct one's own proof-of-concept testing with real-world data. MongoDB is presented as a general-purpose database well-suited for operational workloads, including time-series data, thanks to its flexible document model, transactional consistency, horizontal scaling, native datetime support, and real-time analytics capabilities. The author invites readers to explore MongoDB resources, such as webinars, to learn more about designing effective time-series database applications.