HighFile-scopeC# Plug & play

Optimize database queries with JOINs

Prefer JOINs/eager loading over per-row queries to avoid N+1 patterns.

Why this matters

Reduces round-trips and improves query performance.

Side-by-side examples engineers can pattern-match during review.

Avoid

var orders = await ctx.Orders.ToListAsync();
foreach (var o in orders) o.Customer = await ctx.Customers.FindAsync(o.CustomerId);

Prefer

var orders = await ctx.Orders.Include(o => o.Customer).ToListAsync();

Bad

foreach rows => FindAsync()

Good

Include(x => x.Relation)

From the same buckets as this rule.

Critical
Block risky database migrations (locking ops, downtime risk)
Review SQL/database migrations for operations that can lock large tables or cause downtime. Examples: creating indexes without CONCURRENTLY (Postgres), ALTER COLUMN TYPE on big tables, adding NOT NULL without backfill, long-running updates without batching. Require an online migration strategy (CONCURRENTLY, backfill in batches, dual-write/expand-contract) and a rollback plan.
migrations-backward-compatdatabase-query-performance
High
Add database indexes for query optimization
Index frequently filtered or joined columns and verify with query plans.
database-query-performanceperformance-efficiency
High
Add database indexes for query performance
Index columns used in WHERE/JOIN/ORDER and enforce uniqueness where applicable.
database-query-performance