One quick run can fool you. Here is a small, fixed test you can rerun before and after any index.
Resource Governor Workload Groups and Pools: A Simple Setup Example
Resource Governor workload groups let you limit CPU and memory for competing workloads. This introduction answers what Resource Governor is and why you need it, then shows a full T-SQL setup example.
Columnstore Indexes for Reporting Tables
Columnstore indexes for reporting tables can cut scan work, but clustered and nonclustered designs affect loading and point lookups differently.
Finding the Worst Query in Five Minutes With Query Store
Find the worst query with Query Store totals, compare CPU and duration over the last day, inspect plans, and choose the first tuning target.
Tuning Step One: Capture a Wait Stats Baseline Before Changing Anything
Capture a wait stats baseline, compare two saved snapshots, reject reset intervals, and rank meaningful waits before changing settings.
SQL Server Indexing Basics: SQL in Sixty Seconds #006
SQL Server indexing basics start with the query you want to help. The tests here use a 200,000 row table to compare a scan, a plain index and a covering index, show when SQL Server ignores an index, and measure what three extra indexes cost on an insert.
Optimized Plan Forcing: Cutting Compile Time in SQL Server 2022
Check optimized plan forcing in SQL Server 2022 through scoped configuration and Query Store replay flags, then compare compile duration.