---
title: Cache read-only objects
slug: cms-13/docs/cache-read-only-objects
docTags: 
createdAt: 2026-07-30T20:22:06.928Z
---

Most APIs in Optimizely CMS return read-only instances of objects, such as `IContentLoader.Get<TContentData>` which returns a read-only `IContent` instance.

To make changes to read-only instances, create a writable clone with the `CreateWritableClone` method. This approach has the following advantages:

- **Reduce memory consumption** – Threads serving web requests get the same instance of an object, reducing the number of short-lived objects created.
- **Improve performance** – Returning shared read-only instances offers better performance.
- **Cleaner architecture** – This simplifies the implementation because shared object instances cannot be changed by other threads.

Classes that support read-only implement the `IReadOnly<T>` interface, which is defined as follows:

```csharp
public interface IReadOnly {
  void MakeReadOnly();
  bool IsReadOnly {
    get;
  }
  object CreateWritableClone();
}

public interface IReadOnly<out T>: IReadOnly {
  new T CreateWritableClone();
}
```

The lifecycle of a typical `IContent` instance is as follows:

1. Create the `IContent` instance as mutable (writable).
2. Populate the `IContent` instance with property values.
3. Call the `IReadOnly.MakeReadOnly` method to ensure that all contained objects are made read-only. The object is immutable for the remainder of its lifetime.
4. Add the object to the cache.