Daily micro-tips for C#, SQL, performance, and scalable backend engineering.
CROSS APPLY is the Ferrari of SQL join techniques.It looks fancy, and it really is. 🏎️ ⚡ Why CROSS APPLY Is Amazing 🧠 Lets you join custom row-by-row logic 🚀 Runs faster than correlated subqueries 🔍 Works great with TOP, aggregates & ranking 🪄 Cleaner than temp tables SELECT u.Id, x.LastOrder FROM Users u CROSS […]
Indexes aren’t magic —…but they often look like magic when your query goes 40 sec → 20 ms. ⚡ 🏆 5 Index Types Everyone Should Know 🔹 Clustered Index — defines table order 🔹 Nonclustered Index — fast lookup 🔹 Include Columns — covering index booster 🔹 Filtered Index — tiny but powerful 🔹 Columnstore […]
Parameter sniffing is NOT a bug.It’s SQL Server being too smart… sometimes. 😈 The Problem SQL caches a plan for one parameter and reuses it: EXEC GetOrdersByCustomer @customerId = 1; — cached plan EXEC GetOrdersByCustomer @customerId = 9999; — wrong plan reused ⚠ Symptoms Extreme slowdowns Terrible cardinality estimates “It’s fast for me but slow […]
SELECT * feels convenient……but costs you RAM, CPU, network IO, and index usage. ❌ Why SELECT * Is Dangerous 🧱 Prevents covering index usage 🚚 Sends unnecessary columns over network 🔄 Breaks when columns change 🐢 Slows down joins & scans — ❌ Bad SELECT * FROM Orders; — ✔ Good SELECT Id, OrderDate, Amount […]
Scalar functions look innocent……until your query goes from 50 ms → 12 seconds. — ❌ Never do this inside SELECT SELECT Id, dbo.GetUserScore(Id) FROM Users; 💥 Why They’re Slow ⛓ Executed row-by-row 🚫 Breaks parallelism 📉 Kills execution plans 🐌 Turns queries into RBAR (“Row By Agonizing Row”) ✔ The Fix Use Inline Table-Valued Functions […]
⏳ The 3 Lifetimes 🔵 Singleton → stateless global services 🟢 Scoped → per-request (web default) 🟠 Transient → lightweight, multi-instance ❌ Absolute Rule Never inject a Scoped service into a Singleton. Bad: builder.Services.AddSingleton<MyService>(); // depends on DbContext ❌ ✔ Correct Use factory: builder.Services.AddSingleton<MyService>(sp => new MyService(sp.GetRequiredService<IDbContextFactory<AppDb>>())); 🧠 Why? Prevents stale data Eliminates threading issues […]
The old way: foreach (var user in users) user.IsActive = false; await ctx.SaveChangesAsync(); The modern way: await ctx.Users.Where(x => x.IsActive) .ExecuteUpdateAsync(set => set.SetProperty(p => p.IsActive, false)); ⚡ Benefits 🚀 Single SQL statement 🧼 No tracking overhead 💾 Saves CPU + DB roundtrips 🧩 Perfect for batch jobs + cron workers
Records are still the cleanest way to model immutable domain data. public record Order(int Id, decimal Total, string Status); ❤️ Why Devs Love Records 🔐 Built-in immutability 📝 Value-based equality ✂ Boilerplate goes to zero 🔄 Perfect for event-driven + DDD ⚡ Extra Tip Use with expressions to clone deeply but safely.
Rate limiting used to be hard… now it’s literally one line. app.UseRateLimiter(new() { GlobalLimiter = PartitionedRateLimiter.CreateChained( PartitionedRateLimiter.CreateFixedWindow(10, TimeSpan.FromSeconds(5)) ) }); 🔒 Why You Need It 🛡 Stops brute-force 📉 Protects API throughput ⚙ Cloud-native resilience 🌍 Zero-config distributed support (Redis optional) 🧠 Bonus Pair with Minimal APIs for super-light API services.
🌀 Why Async Streams Shine Async Streams (IAsyncEnumerable<T>) are perfect for streaming data without memory blows. await foreach (var log in service.GetLogsAsync()) { Console.WriteLine(log); } ✨ What They Solve 🔁 Handling live logs 📡 Streamed API responses 🧵 Reducing memory spikes 🌊 Backpressure-friendly async flow 💡 Pro Tip Combine with channels for ultra-responsive pipelines.