A database that responds in 10 seconds where it used to respond in 100 milliseconds isn't just a technical problem — it's a business problem. Users get frustrated, applications fail, and productivity drops. Worse, performance usually degrades gradually, almost imperceptibly, until the system collapses.
At Datandina we regularly audit and optimize SQL Server, PostgreSQL, and MySQL databases. These are the 5 most common causes of slowness and how to fix them.
1. Missing Indexes (or Poorly Designed Ones)
An index in a database is equivalent to a book's index: instead of reading all pages to find a concept, you go directly to the right page.
How to detect it: Run the execution plan of your slowest queries. If you see "Full Table Scan" or "Seq Scan" on large tables, an index is missing.
Solution: Create indexes on columns that appear in WHERE, JOIN, and ORDER BY clauses of the most frequent queries.
2. N+1 Queries
The N+1 problem occurs when to fetch a list of N records, the application executes N+1 database queries — one for the list and one for each item.
Classic example: displaying a list of 100 orders with each customer's name. If the code makes one query for orders and then 100 individual queries for each customer, it's executing 101 queries where it should be 1.
Solution: use JOINs to bring all information in a single query, or implement eager loading in the ORM.
3. Outdated Statistics
The database engine uses statistics about data distribution to choose the most efficient execution plan. If those statistics are outdated, the engine may choose a suboptimal plan.
Solution: run UPDATE STATISTICS (SQL Server) or ANALYZE (PostgreSQL) regularly, especially on high-volume tables.
4. Long Transactions and Locks
A transaction that takes too long to complete blocks resources that other queries need, creating a chain of waits that can paralyze the system.
Solution: review long transactions and split them into smaller operations. Implement timeouts. Review transaction isolation levels.
5. Insufficient Hardware and Configuration
Sometimes the problem isn't the SQL code but the server configuration. A database with insufficient RAM forced to do many disk operations will perform far below its potential.
Is your database experiencing performance issues? Contact us for an initial audit.