Background In Part 1, we established that access patterns & not entities should drive your design. In Part 2, we fixed the database by replacing brittle three-table JOINs with a covering index, reducing P99 on the listing query. The schema was right. The index was right. The listing API itself was fast. And then it …

Background In the first part we established the foundational principle that separates systems which survive scale from systems that collapse under it - design for access patterns, not for entities. In this second part we double click on the database design of the User Profile system and try to understand its impact …