https://learn.microsoft.com/en-us/sql/relational-databases/sql-server-index-design-guide https://learn.microsoft.com/en-us/sql/relational-databases/s... This o

https://learn.microsoft.com/en-us/sql/relational-databases/sql-server-index-design-guide https://learn.microsoft.com/en-us/sql/relational-databases/s... This one is a classic for MSSQL, most of it is applicable on postgres.