Serializable ​

Serializable is the strictest isolation level. Under the Serializable isolation level, all transactions are executed in a sequential order, which prevents dirty reads, non-repeatable reads, and phantom reads from occurring.

Characteristics ​

While the Serializable isolation level provides the highest level of safety for transactions, it comes at the cost of efficiency. Since transactions are executed serially, this can significantly reduce application performance. For most scenarios that do not require such strict isolation, the Serializable level is generally not used.

Default Isolation Level ​

If no isolation level is specified, the database will use a default isolation level. In MySQL, when using InnoDB, the default isolation level is Repeatable Read.