What is a B-tree index?

A B-tree index is a data structure used in databases for fast searching, inserting, and deleting data. B-tree (a balanced tree with multiple keys in a node) is optimized for working with large volumes of data on disk.

Main characteristics of a B-tree index:

• Each node contains multiple keys and child pointers, reducing the tree's height and the number of disk accesses.
• The tree is balanced: all leaf nodes are on the same level.
• It allows efficient search, insert, and delete operations in logarithmic time.

In a database, a B-tree index stores keys and references to the corresponding records, which speeds up queries with search conditions, sorting, and range queries.

Example: if you have a table with millions of records and an index on the "id" field, a B-tree index will allow you to quickly find the needed record without scanning the entire table.