# Raft algorithm: What's the meaning of concept index?

When reading the description of Raft algorithm from Wikipedia, I noticed there is a special word index.

For web developer, index usually refers to database index.

• When it comes to Raft algorithm, what does index mean? Is it similar with database index? e.g. B+ tree.

• What is raft index used for?

Wikipedia: Raft

Log Matching: if two logs contain an entry with the same index and term, then the logs are identical in all entries up through the given index.

https://en.wikipedia.org/wiki/Raft_(computer_science)#Safety_rules_in_Raft

• Presumably each log entry has an index. – Yuval Filmus Sep 20 '18 at 3:34

"For web developer, index usually refers to database index." It looks like that you come with a training in computer databases. As a web developer myself, I would not agree with you readily at all. Indices are used much more frequently to access array elements in everyday programming in just about every programming language. For example, in JavaScript, if there is an array persons=["alice", "bob", "Diego"], then we can use index 1 to access its second element "bob", persons[1]. You will find the same or similar usage that are also abundant in Java, C, C++, C#, Python, Ruby, Go, etc.