What circumstances can lead to delays in data reading, besides using indexes?

Delays in reading data can occur for various reasons besides the absence or ineffective use of indexes:

• Locks and resource contention: if multiple transactions try to read or write the same data simultaneously, waiting may occur.
• Large data volume: reading a large number of rows or columns without filtering increases execution time.
• Low disk subsystem performance: slow SSDs or HDDs, high disk load.
• Network delays: if the database is remote, network latency affects data retrieval speed.
• Unoptimized queries: complex JOINs, subqueries, lack of filters.
• Caching: absence or ineffective use of cache leads to repeated disk access.
• Server configuration and parallelism: insufficient CPU, memory resources, incorrect connection pool settings.

To diagnose, use query profiling and database monitoring tools.