---
title: Cache objects
slug: cms-11/dev-docs/object-caching
docTags: 
createdAt: 2026-07-22T19:45:22.664Z
---

The `IObjectInstanceCache` and `ISynchronizedObjectInstanceCache` interfaces expose the built-in cache system with custom dependency and eviction policies. Optimizely Content Management System (CMS) and Optimizely Customized Commerce use these interfaces to cache content and system data, and you can use the interfaces to cache custom data. The `ISynchronizedObjectInstanceCache` interface synchronizes cache removal among servers in a load-balanced environment using the [Event management](docId\:qbbi2X0ioj79Gdvj5egId) system.

:::hint{type="info"}
**Note**
If you were using the `CacheManager` class in CMS, you should take a dependency on `ISynchronizedObjectInstanceCache` instead, because the new interface provides the same functionality. The `IObjectInstanceCache` supersedes `IRuntimeCache` (that was previously used only by CMS) because it supports different cache implementations by abstracting the `CacheDependency` class and other things.
:::

## CacheEvictionPolicy

Use the `CacheEvictionPolicy` class for object caching because it is de-coupled from any specific cache implementation. `CacheEvictionPolicy` is immutable so that you can reuse existing instances of the class. (The `CacheDependency` class is tightly coupled to the `HttpRuntime` implementation, and if you want to have a custom cache implementation, you cannot rely on `CacheDependency`.) The following example shows how to use `CacheEvictionPolicy`.

```csharp
public void AddToCache(string key, object val) {
    // If you don't care about specific cache management, use CacheEvictionPolicy.Empty
    _cache.Insert(key, val, CacheEvictionPolicy.Empty);

    // To enable sliding expiration for 10s, depending on "otherKey"
    _cache.Insert(key, val, new CacheEvictionPolicy(
        new string[] {
          "otherKey"
        }, // Cache key dependency
        new TimeSpan(0, 0, 10), // Always a timespan for timeouts
        CacheTimeoutType.Sliding);
    }
```

## Master keys

When you need to define a common dependency for cached data, create a master dependency (or master key) with `CacheEvictionPolicy`, which automatically adds a list of key names to the cache as regular entries. Doing so means you do not need to add code to conditionally add these entries before inserting specific data into the cache.

In the following example, the difference between the cache key dependency and the master key dependency is that if there is no `otherKey` in the cache, the data is not inserted. If there is no entry with `MasterKey`, then it adds a dummy value with the given key, thus letting you insert the data.

```csharp
public void AddToCacheWithMasterDependency(string key, object val) {
    // To enable absolute expiration for 5 minutes, depending on "otherKey" and master key dependency to "MasterKey"
    _cache.Insert(key, val, new CacheEvictionPolicy(
        null, // No file dependencies
        new string[] {
          "otherKey"
        }, // Cache key dependency
        new string[] {
          "MasterKey"
        }, // Master key dependency
        new TimeSpan(0, 5, 0), // Always a timespan for timeouts
        CacheTimeoutType.Absolute);
    }
```