Why Does Using an ORM Decrease Database Performance?

While trying to optimize the shipping module in a production ERP, I noticed that database queries were incredibly slow. At first, I examined the SQL queries and checked the indexes. However, I couldn't get the performance boost I expected. The problem lay in the Object-Relational Mapper (ORM) library, which was the cornerstone of our application. ORMs make things easier for software developers by providing an abstract layer for database operations, but this convenience often comes at a performance cost. In this post, I will explain why using an ORM decreases database performance, using concrete examples from my own field experience.

The core promise of ORMs is to keep developers away from SQL and allow them to interact with databases in a way that is more aligned with the object-oriented paradigm. This is a huge advantage, especially in small and medium-sized projects or rapid prototyping processes. However, when things get complex and performance becomes critical, the efficiency of the queries generated by ORMs starts to be questioned. In many cases I have encountered, especially in enterprise software development processes, the default behaviors of ORMs created an unexpected load on database servers.