Advances in Indexing Techniques for Database Systems a Systematic Literature Review

Indexing is one of the most important mechanisms for improving query performance in database systems. Without a proper index, even simple queries can become extremely slow when dealing with large amounts of data. This paper reviews the main indexing techniques used in modern databases from classical tree-based and hash-based structures to bitmap indexes and distributed approaches suited for big data environments. For each technique, the underlying principles, performance characteristics, and limitations are analysed. The paper also includes a comparison table and a discussion of recent trends, such as learned index structures and AI-assisted query optimization. The main takeaway is straightforward: there is no universally best index the right choice always depends on the workload, the data, and the system architecture.