ACID Transactions: What’s the Meaning of Isolation Levels for Your Application

ACID transactions are fundamental to database systems, ensuring data integrity through properties like Atomicity, Consistency, Isolation, and Durability. Isolation levels, which determine the interaction between concurrent transactions, are crucial for maintaining data consistency in multi-user environments. Lower isolation levels, such as Read Uncommitted, can lead to issues like dirty reads, while higher levels like Serializable ensure data integrity but may reduce performance. Snapshot Isolation is proposed as a sensible default for balancing consistency and performance, as it provides a consistent view of the database while allowing for concurrency. However, even the highest isolation levels cannot resolve all concurrency issues, emphasizing the need for careful application-level error handling. Memgraph, for instance, uses Snapshot Isolation as its default, ensuring high data consistency with multiversion concurrency control, while also offering lower isolation levels for performance trade-offs and an analytical mode for lower memory usage without guaranteeing data consistency.