What are Compiled Queries in EF Core, and when are they worth using?

Short answer

They compile a LINQ expression tree into a ready-to-use delegate, avoiding the cost of analyzing and translating the same LINQ query to SQL on repeated calls.

Explanation

EF Core caches generated SQL queries, but it still spends a small amount of time matching the LINQ expression tree and building the execution plan on every call. With EF.CompileAsyncQuery(), the query is compiled once in a static field and executed directly, approaching the response times of micro-ORMs such as Dapper on frequently used critical paths.

Code example

private static readonly Func<AppDbContext, int, Task<User?>> GetUserCompiled =
    EF.CompileAsyncQuery((AppDbContext db, int id) =>
        db.Users.AsNoTracking().FirstOrDefault(u => u.Id == id));

// High-performance usage:
var user = await GetUserCompiled(dbContext, userId);

Common mistakes

• Compiling every application query in advance without a real need, adding complexity when it is useful only for Hot Paths.

Follow-up questions

• How do ExecuteUpdate and ExecuteDelete in EF Core 7+ improve performance for bulk operations?

Sources

• Microsoft Learn — Compiled queries in EF Core