Distributed Caching in ASP.NET Core

Introduction

As web applications scale, repeatedly retrieving the same data from a database can increase response times and place unnecessary load on backend services. While in-memory caching improves performance for a single application instance, it becomes less effective in distributed environments where multiple servers handle incoming requests.

Distributed caching solves this challenge by storing cached data in a centralized cache that is shared across all application instances. ASP.NET Core provides built-in support for distributed caching, making it easy to integrate technologies such as Redis and SQL Server into modern applications.

In this article, you'll learn what distributed caching is, how it works in ASP.NET Core, and the best practices for building scalable and high-performance applications.

What Is Distributed Caching?

A distributed cache stores data in a shared location that can be accessed by multiple application instances.

Unlike in-memory caching, the cached data remains consistent across all servers.

Common distributed cache providers include:

Azure Cache for Redis
Redis
SQL Server
NCache

Distributed caching is particularly useful in load-balanced and cloud-hosted environments.

Why Use Distributed Caching?

Without a shared cache, each application instance maintains its own cache, leading to inconsistent data and duplicate database queries.

Distributed caching provides several advantages:

Faster response times
Reduced database load
Shared cache across servers
Better scalability
Improved application performance
Consistent cached data

These benefits make distributed caching an important component of modern web applications.

In-Memory Cache vs Distributed Cache

The following table compares the two approaches.

Feature	In-Memory Cache	Distributed Cache
Shared Across Servers	No	Yes
Suitable for Load Balancing	No	Yes
Performance	Very Fast	Fast
Data Persistence	No	Depends on Provider
Scalability	Limited	Excellent

Choose distributed caching when your application runs on multiple servers or containers.

Install the Redis Cache Package

ASP.NET Core provides a Redis implementation of IDistributedCache.

Install the required package.

dotnet add package Microsoft.Extensions.Caching.StackExchangeRedis

This package enables Redis integration with the built-in distributed cache abstraction.

Configure Distributed Cache

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddStackExchangeRedisCache(options =>
{
    options.Configuration = "localhost:6379";
    options.InstanceName = "MyApp:";
});

The application can now use IDistributedCache through dependency injection.

Inject IDistributedCache

Inject the distributed cache into your service or controller.

using Microsoft.Extensions.Caching.Distributed;

public class ProductService
{
    private readonly IDistributedCache _cache;

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

The IDistributedCache interface provides a consistent API regardless of the underlying cache provider.

Store Data in the Cache

Save a value using SetStringAsync.

await _cache.SetStringAsync(
    "Product:101",
    "Gaming Laptop");

The value becomes available to every application instance connected to the same cache.

Retrieve Cached Data

Read the cached value.

var product =
    await _cache.GetStringAsync("Product:101");

If the key exists, the cached value is returned immediately without querying the database.

Configure Expiration

Always define an expiration policy for cached data.

var options = new DistributedCacheEntryOptions
{
    AbsoluteExpirationRelativeToNow =
        TimeSpan.FromMinutes(30)
};

await _cache.SetStringAsync(
    "Product:101",
    "Gaming Laptop",
    options);

Expiration prevents stale data from remaining in the cache indefinitely.

Cache Complex Objects

Applications often cache complete objects instead of simple strings.

Serialize the object before storing it.

var json = JsonSerializer.Serialize(product);

await _cache.SetStringAsync(
    "Product:101",
    json);

Retrieve and deserialize it later.

var json =
    await _cache.GetStringAsync("Product:101");

var product =
    JsonSerializer.Deserialize<Product>(json!);

JSON serialization is a common approach for caching domain models.

Implement the Cache-Aside Pattern

The Cache-Aside pattern is one of the most widely used caching strategies.

The workflow is:

Check the cache.
If the data exists, return it.
If the data is missing, query the database.
Store the result in the cache.
Return the data to the caller.

This pattern minimizes unnecessary database access while keeping frequently requested data readily available.

Choose Appropriate Expiration Policies

Different types of data require different cache lifetimes.

Examples include:

Product catalog: 30–60 minutes
Application settings: Several hours
User profiles: 10–30 minutes
Session data: Based on session timeout

Selecting appropriate expiration values helps balance performance and data freshness.

Monitor Cache Performance

Track cache usage to ensure your caching strategy is effective.

Useful metrics include:

Cache hit rate
Cache miss rate
Memory usage
Response time
Evictions
Connection status

Regular monitoring helps identify opportunities for optimization.

Best Practices

When implementing distributed caching in ASP.NET Core:

Cache frequently requested data.
Use meaningful cache keys.
Configure expiration for every cached item.
Keep cached objects reasonably small.
Use the Cache-Aside pattern.
Serialize objects efficiently.
Monitor cache performance regularly.
Secure Redis connections using TLS and authentication.
Remove or refresh cached data after important updates.

These practices help maximize performance while maintaining data consistency.

Common Mistakes to Avoid

Avoid these common caching mistakes:

Caching every database query.
Using inconsistent cache key naming.
Forgetting to configure expiration policies.
Storing excessively large objects.
Ignoring cache invalidation after data updates.
Treating the cache as permanent storage.
Failing to monitor cache health and performance.

A well-designed caching strategy improves both performance and reliability.

Distributed Cache vs In-Memory Cache

The following comparison highlights when each approach is most appropriate.

Scenario	In-Memory Cache	Distributed Cache
Single Server Application	✓	✓
Multiple Application Instances	✗	✓
Cloud Deployments	Limited	✓
Load-Balancing	✗	✓
Shared Session Data	✗	✓

Using the right caching approach depends on your application's architecture and scalability requirements.

Conclusion

Distributed caching is an essential technique for improving the performance and scalability of ASP.NET Core applications running in distributed or cloud environments. By storing frequently accessed data in a shared cache, you can reduce database load, improve response times, and ensure consistent data across multiple application instances.

By following best practices such as using the IDistributedCache abstraction, implementing the Cache-Aside pattern, configuring appropriate expiration policies, and monitoring cache performance, you can build high-performing, scalable applications that deliver a responsive experience to users.