Daily micro-tips for C#, SQL, performance, and scalable backend engineering.
Many devs struggle with strongly-typed configuration returning null unexpectedly. 🔥 Main Causes Missing services.Configure<T>() Wrong section name Mistyped property names Missing getters/setters Nested classes not matching JSON structure ✔ The Correct Pattern builder.Services.Configure<MySettings>( builder.Configuration.GetSection(“MySettings”)); public class MySettings { public string ApiKey { get; set; } } ✔ But Here’s the Hidden Trick Add validation to […]
This is one of the most painful production issues:async calls sometimes never complete under high load. 🔍 Root Cause: ThreadPool Starvation + Sync-over-Async If your code blocks threads, the async continuations never get a chance to run. Task.Run(() => { Thread.Sleep(3000); // ❌ Blocks threadpool }); Eventually, under load: Tasks queue up ThreadPool can’t spawn […]
Most devs don’t know that Grid can inherit layout from its parent grid. .child { display: grid; grid-template-columns: subgrid; } 🔥 Why It’s Huge Perfect alignment between parent & child Cleaner responsive layouts No duplicated breakpoints Layout consistency made easy
Service Workers let your site work offline, cache assets, and load instantly. navigator.serviceWorker.register(‘/service-worker.js’); ✨ What You Get ⚡ Near-instant load time 📦 Cached static assets 📡 Offline browsing 🔋 Reduced server load 💡 Combine with “cache-first” strategies for ultimate speed.
🎯 Debounce Trigger after user stops typing. Great for: Search boxes Auto-suggest Validation 🌀 Throttle Trigger every X ms, no matter what. Great for: Scroll events Resize events Mouse move Quick Example const debounced = debounce(fn, 300); const throttled = throttle(fn, 200); 💡 Using the wrong one leads to janky UI & wasted CPU.
Many APIs slow down because lifetime choices are wrong. ❌ Common Mistake Using Transient for heavy services: services.AddTransient<EmailService>(); ✔ Correct Use Singleton for stateless services: services.AddSingleton<IEmailSender, EmailService>(); 💡 Why? Fewer allocations Less GC pressure Faster resolving More consistent performance
Kestrel has built-in protection against floods, slow clients, and excessive headers. Key Settings in appsettings.json: “Kestrel”: { “Limits”: { “MaxRequestBodySize”: 1048576, “KeepAliveTimeout”: “00:00:30”, “RequestHeadersTimeout”: “00:00:30” } } 💡 Why This Matters Stops slow-loris attacks Reduces memory pressure Prevents API overload Ensures predictable scaling Bonus Enable HTTP/2 for better concurrency.
🔒 Blocking Queries wait for each other Slow performance Not fatal ✔ How to Fix Blocking Correct indexing Reduce long transactions Avoid row locks with better filters 💥 Deadlocks Two queries wait on each other SQL kills one session Returns error 1205 ✔ Fix Deadlocks Always access tables in SAME ORDER Keep transactions very […]
SARG (Search ARGument Able) is the biggest reason queries go from 20ms → 10 seconds. ❌ Non-SARGable WHERE YEAR(OrderDate) = 2024 This forces a full scan. ✔ SARGable Version WHERE OrderDate >= ‘2024-01-01’ AND OrderDate < ‘2025-01-01’ 💡 Why It Matters Enables index seeks Saves CPU Reduces IO dramatically
In high concurrency, ThreadPool starvation causes tasks to freeze for seconds. ⚠ The Symptoms Slow responses under load Random spikes Async operations timing out 😬 Common Cause Task.Run(() => { Thread.Sleep(2000); // ❌ Blocks the threadpool }); ✔ The Fix Use true async APIs: await Task.Delay(2000); 💡 Bonus Use ThreadPool.GetAvailableThreads to diagnose starvation.
Unsubscribed event handlers are one of the biggest real-world leak causes. publisher.SomeEvent += OnEvent; // stays forever if not removed ⚠ Why It Leaks The publisher holds a reference to your object GC can’t collect your object Memory keeps climbing ✔ The Fix Always unsubscribe: publisher.SomeEvent -= OnEvent; Or use weak events or IDisposable patterns. […]
Deadlocks in async/await often come from sync-over-async and the UI/ASP.NET synchronization context. var data = GetDataAsync().Result; // ❌ Possible deadlock 🔥 Why This Happens The UI thread waits Async method tries to resume on the UI thread Both wait forever 😅 ✔ The Fix Use ConfigureAwait(false) in library code: await SomeLibraryCall().ConfigureAwait(false); 💡 Pro Tips Never […]
Most API latency problems = opening too many SQL connections. 🚀 Fix Use a single pooled client: builder.Services.AddDbContext<AppDb>(options => options.UseSqlServer(connString, o => o.EnableRetryOnFailure())); ✨ Benefits ⚡ Fast connection acquisition 📉 Lower CPU 🧵 Stable high-load behavior 💡 BonusUse Max Pool Size=200 in connection string for heavy systems.
Filters allow cross-cutting logic without writing a full middleware. builder.Services.AddEndpointFilter<ValidationFilter>(); ⚡ Why They’re Great ⚙ Less overhead 🎯 Scoped to specific endpoints 🧽 Cleaner architectures 🔍 Perfect for validation, auth, logging
Web Workers allow JS to run CPU-heavy tasks off the main thread. const worker = new Worker(“worker.js”); worker.postMessage({ action: “process” }); 💥 Why Use Them 🧵 Prevent UI blocking 🚀 Faster data processing 📸 Smooth animations 🧩 Perfect for image, crypto & data tasks
Lazy loading is now native in all modern browsers. <img src=”hero.jpg” loading=”lazy” /> 🚀 Why It’s Amazing 📉 Instant LCP improvements 🧠 Saves bandwidth ⚡ Faster page loads 🛠 No JS required
Media queries scale by viewport…Container queries scale by component. .card { container-type: inline-size; } @container (min-width: 450px) { .card { flex-direction: row; } } ✨ Why They’re a Big Deal 🎯 Component-level responsiveness 📦 No more giant breakpoint spaghetti 🧩 Perfect for design systems
Window functions eliminate messy subqueries and temp tables. SELECT UserId, Amount, RANK() OVER (ORDER BY Amount DESC) AS RankNo FROM Orders; ⚡ Why They’re Amazing 🚀 Blazingly fast 🧮 Ideal for analytics 🔍 Cleaner than GROUP BY hacks ✂ Replaces many procedural patterns
Most devs rebuild indexes far too often. ✔ What Matters 📉 Fragmentation < 30% → ignore 🔄 30–80% → reorganize 🔨 > 80% → rebuild ⚡ Better Approach Use sys.dm_db_index_physical_stats to target heavy tables only. SELECT index_type_desc, avg_fragmentation_in_percent FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, ‘LIMITED’); 💡 Pro Tip “Rebuild everything nightly” is anti-pattern — kills IO.
Most devs still use the outdated AES CBC mode.Use AesGcm for modern authenticated encryption. using var aes = new AesGcm(key); aes.Encrypt(nonce, data, ciphertext, tag); 🛡 Why It’s Better ✔ Authenticated ✔ Fast on modern CPUs ✔ Built to prevent tampering ✔ Recommended for APIs & tokens
Source Generators remove runtime reflection overhead by generating code during compilation. [MySerialize] public class Product { public string Name { get; set; } } 🚀 Benefits 🧵 Zero runtime reflection ⚙ Blazing-fast mappers & DTO serializers 💾 Smaller memory footprint 🧩 Perfect for AOT workloads (.NET NativeAOT)
Span<T> gives C# ultra-fast, stack-only slicing without copying memory. Span<char> slice = name.AsSpan(0, 3); ⚡ Why It Matters 🧠 Zero GC allocations 🚀 Safe low-level memory access 📉 Faster parsing, CSV handling, protocol processing ♻ Ideal for high-throughput APIs 💡 Pro Tip Combine with ReadOnlySequence<T> for pipelines.
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.