Every backend developer has typed ->index() in a migration at some point. Fewer have stopped to ask: what does the database engine actually do with that? This article walks through indexes from first principles — B+Trees, how MySQL decides whether to use an index at all, why column order in a c...
Source: [Dev.to](https://dev.to/ali_algmass/database-indexes-whats-actually-happening-under-the-hood-2bin)