Transactions are anything but straightforward, with each database vendor offering its unique interpretation of the term. By scrutinising the internal architectures of these databases, engineers can gain valuable insights, enabling them to write more stable applications.This talk explores the intricacies of transactions, focusing on modern databases. Delving into distributed transactions, we discuss network challenges and cloud deployments in the contemporary era. The session provides a concise examination of the internal architectures of cloud-scale, multi-tenant databases such as Spanner, DynamoDB, and Amazon Aurora.