EFCore.QueryGuard 1.0.0

EFCore.QueryGuard

A lightweight EF Core interceptor that detects common query problems at runtime — before they hit production.

• N+1 detection — flags when the same query pattern repeats above a configurable threshold
• Slow query alerts — warns when individual queries exceed a time threshold
• Excessive query count — catches scopes with too many queries (e.g., loops that should be batched)

Installation

dotnet add package EFCore.QueryGuard

For ASP.NET Core middleware integration:

dotnet add package EFCore.QueryGuard.AspNetCore

Quick Start

In your DbContext

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    optionsBuilder
        .UseSqlServer(connectionString)
        .UseQueryGuard(options =>
        {
            options.SlowQueryThresholdMs = 300;
            options.DetectNPlusOne = true;
            options.NPlusOneThreshold = 3;
        });
}

In ASP.NET Core (Program.cs)

// Register the interceptor and options
builder.Services.AddQueryGuard(options =>
{
    options.SlowQueryThresholdMs = 200;
    options.DetectNPlusOne = true;
});

// Register your DbContext, wiring in the interceptor
builder.Services.AddDbContext<AppDbContext>((sp, options) =>
{
    var interceptor = sp.GetRequiredService<QueryGuardInterceptor>();
    options.UseSqlServer(connectionString)
           .AddInterceptors(interceptor);
});

// Add middleware — wraps each HTTP request in a QueryGuard scope
app.UseQueryGuard();

Each HTTP request is automatically wrapped in a scope. Violations are logged as warnings and surfaced via the X-QueryGuard-Violations: {count} response header.

Configuration

All options are set via QueryGuardOptions:

What Violations Look Like

QueryGuard logs violations at Warning level via ILogger:

warn: EFCore.QueryGuard.QueryGuardInterceptor
      [QueryGuard:NPlusOne] N+1 query detected: same query pattern executed 3 times (threshold: 3): SELECT "p"."Id", "p"."Name" FROM "Products" AS "p" WHERE "p"."CategoryId" = @__id_0

warn: EFCore.QueryGuard.QueryGuardInterceptor
      [QueryGuard:SlowQuery] Slow query detected (612ms > threshold 500ms): SELECT "p"."Id", "p"."Name", "p"."Price" FROM "Products" AS "p"

warn: EFCore.QueryGuard.QueryGuardInterceptor
      [QueryGuard:ExcessiveQueryCount] Excessive query count: 11 queries executed in scope (max: 10)

When using the ASP.NET Core middleware, violations are also reflected in the response header:

X-QueryGuard-Violations: 3

License

MIT — see LICENSE.