How do database indexes speed up the search for records?

Database indexes speed up the search for records by functioning much like the index of a book, allowing for efficient random access to data rather than requiring a slow, sequential scan of an entire file.1

An index contains a key for each record along with the specific location where that record is stored. Because these indexes can be quite large, they are typically organized in a hierarchical, treelike structure. This structure allows the system to navigate efficiently to the desired record by traversing the tree—for example, by pointing to sub-indexes based on alphabetical prefixes—rather than searching through every individual record in the database. By using these pointers to locate data directly, the system significantly reduces the time and processing power required to retrieve specific information.1