As a developer, it is crucial to understand Isolation Levels and Multi-Version Concurrency Control (MVCC) to create scalable applications without compromising data integrity due to race conditions. Although the default isolation level in most databases is usually adequate, it is important to know and use it correctly in your application. This technical session explores the implementation of these concepts in popular SQL databases such as Oracle, MySQL, SQL Server, PostgreSQL, and YugabyteDB. We will also examine why traditional SQL standard definitions may not be suitable for MVCC databases and why this knowledge is essential for developers. By the end of the session, you will be able to navigate these subtleties with ease and make informed decisions in your application design without getting too academic.