.Net

💡 What Is Caching?

Caching means storing frequently used data in a fast place (memory or a dedicated cache server) so you don’t have to recalculate or re-fetch it every time.

Think of it like keeping your most-used tools on your desk instead of running to the garage each time.

🎯 Why Use Caching?

⚡ Speed: Faster responses for users.
💰 Cost: Fewer database or API calls → saves money.
🔒 Resilience: Can serve data even if the database is slow or temporarily down.

🏷️ Common Types of Caching

1. In-Memory Cache

Data stored inside the app’s memory (RAM).
Super fast but cleared when the app restarts or scales out to multiple servers.
.NET Example: IMemoryCache (built into ASP.NET Core).


services.AddMemoryCache();


public class ProductService
{
    private readonly IMemoryCache _cache;

    public ProductService(IMemoryCache cache)
    {
        _cache = cache;
    }

    public Product GetProduct(int id)
    {
        return _cache.GetOrCreate($"product_{id}", entry =>
        {
            entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(10);
            return LoadProductFromDatabase(id);
        });
    }
}

2. Distributed Cache

Shared cache for multiple servers/instances.
Good for cloud or load-balanced apps.
Examples: Redis, SQL Server cache, NCache.


services.AddStackExchangeRedisCache(options =>
{
    options.Configuration = "localhost:6379";
});

3. Output/Response Caching

Cache the whole HTTP response.
Useful for pages or APIs that don’t change often.


[ResponseCache(Duration = 60)]
public IActionResult GetWeather() => Ok(weatherData);

4. Client-Side/Browser Cache

Store static files (images, CSS, JS) or API responses in the browser.
Controlled with HTTP headers (Cache-Control, ETag).

🧠 Cache Strategies

Absolute Expiration: Cache expires after a fixed time (e.g., 10 minutes).
Sliding Expiration: Reset the timer every time the data is accessed.
Cache Aside (Lazy Loading): Check cache first; if not present, load from source and add to cache.
Write-Through / Write-Behind: Write data to the cache and database at the same time or asynchronously.

⚠️ Things to Watch

Stale Data: Data might become outdated—set expiration wisely.
Cache Invalidation: Decide how/when to remove or refresh data.
Memory Limits: Monitor size to avoid crashes or evictions.

✅ Quick Best Practices

Cache only expensive or frequently used data.
Use distributed caching for scalable web apps.
Monitor hit/miss rates and memory usage.
Protect sensitive data—don’t cache private info carelessly.

🏁 Recap

Caching = storing frequently used data for quick reuse.

Type	Where stored	Example in .NET
In-Memory	App memory	`IMemoryCache`
Distributed	External server	Redis, SQL Server
Output/Response	Web/API responses	`[ResponseCache]`
Client/Browser	User’s browser	Cache headers

By combining the right caching type and strategy, you can make your .NET apps faster, cheaper, and more reliable.

Monday, 22 September 2025

Caching