Caching Strategies in ASP.NET Core (In-Memory vs Distributed)
💡 Concept Name
Caching Strategies: In-Memory & Distributed
📘 Quick Intro
Caching is a way to store data temporarily to reduce database or API calls. ASP.NET Core supports In-Memory and Distributed caching mechanisms. In-Memory is simple and fast, but works only within a single server. Distributed cache like Redis allows sharing across servers.
🧠 Analogy / Short Story
Think of In-Memory cache like a whiteboard on your desk — quick to access but only for you. If your desk moves (server restarts), data is lost. Distributed cache is like a shared cloud drive — accessible from multiple desks (servers) and persists even if one machine fails.
🔧 Technical Explanation
ASP.NET Core offers two built-in cache interfaces: `IMemoryCache` for local caching and `IDistributedCache` for external stores like Redis or SQL Server.
Caching reduces server load and response time. Data can be stored with expiration settings like absolute or sliding expiration. Use distributed caching for scalable apps and clustered environments.
🎯 Purpose & Use Case
- ✅ Improve performance by reducing repetitive DB calls
- ✅ Store frequently accessed configuration or query results
- ✅ Enable scalable caching across multiple servers (Distributed)
- ✅ Reduce latency for read-heavy APIs
- ✅ Persist cache even after server restarts (Distributed)
💻 Real Code Example
// In-Memory Caching Setup
builder.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 FetchProductFromDb(id); // Simulate DB call
});
}
}
// Distributed Cache Setup (Redis)
builder.Services.AddStackExchangeRedisCache(options =>
{
options.Configuration = "localhost:6379";
});
❓ Interview Q&A
Q1: What is In-Memory Caching?
A: Local cache stored in server RAM, fast but non-distributed.
Q2: What is Distributed Caching?
A: External caching system (e.g., Redis) accessible across servers.
Q3: Which interface does In-Memory cache use?
A: `IMemoryCache`
Q4: Which interface does Distributed cache use?
A: `IDistributedCache`
Q5: Can you use expiration in cache?
A: Yes, using absolute and sliding expiration options.
Q6: When to prefer Distributed cache?
A: When running in multi-server environments or needing persistence.
Q7: Name a popular Distributed cache system.
A: Redis
Q8: Is caching secure for sensitive data?
A: Not recommended unless encrypted and protected.
Q9: Can we use both caches together?
A: Yes, depending on data type and need.
Q10: How to clear a specific cache item?
A: Use `Remove(key)` method of the cache service.
📝 MCQs
Q1. Which interface is used for In-Memory cache?
- IDistributedCache
- ICacheService
- IMemoryCache
- ICacheManager
Q2. Which caching is suitable for distributed apps?
- Memory Cache
- Session Cache
- Cookie Cache
- Distributed Cache
Q3. What is used to cache data for 10 minutes?
- CacheTimeout
- SlidingExpiration
- FixedExpiration
- AbsoluteExpirationRelativeToNow
Q4. Which system is commonly used for distributed cache?
- MongoDB
- MySQL
- Redis
- SQLite
Q5. Is In-Memory cache shared across servers?
- Yes
- No
- Sometimes
- Only with Redis
Q6. How do you remove a cached item?
- cache.Clear()
- cache.Flush()
- cache.Remove(key)
- cache.DeleteAll()
Q7. What happens to In-Memory cache after restart?
- Data persists
- Data syncs
- It is cleared
- It auto-saves
Q8. Which caching is best for high-availability?
- Session
- In-Memory
- Distributed
- None
Q9. Where does `IDistributedCache` store data?
- Client browser
- Memory
- Temp folder
- External systems like Redis
Q10. Which cache allows `GetOrCreate()` method?
- IDistributedCache
- IMemoryCache
- ICacheHelper
- ICustomCache
💡 Bonus Insight
Use cache thoughtfully. Never cache sensitive data unless encrypted. Also consider cache busting strategies to avoid serving stale data to users.
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