Why did you have to engage in SQL optimization, and how were responsibilities divided between data engineers and developers?

SQL optimization is often necessary to improve query performance, especially when working with large volumes of data or complex analytical tasks. For example, optimization may include:

• Rewriting queries to reduce the number of JOIN operations or subqueries.
• Using indexes and analyzing execution plans.
• Breaking down large queries into simpler ones.

In the division of responsibilities between data engineers and developers:

• Data engineers are responsible for building and maintaining data infrastructure, creating efficient ETL processes, and optimizing data storage and processing at the database and data platform levels.
• Developers write business logic and applications, use ready-made queries, and can optimize queries within their services, but do not engage in deep infrastructure optimization.

This delineation helps focus efforts and utilize each team's expertise most effectively.