# How do you implement versioning in a document database?

Source: https://zilliz.com/ai-faq/how-do-you-implement-versioning-in-a-document-database
Author: zilliz

Implementing versioning in a document database can be achieved through several approaches, depending on the requirements of your application. One common method is to store each version of a document as a separate document in a collection. For example, if you have a document representing a user's profile, you could create a new document for each update, including a version number or timestamp as part of the document's structure. This way, you maintain a complete history of changes, and retrieving past versions is straightforward.

Another approach is to use embedded documents or arrays within a single document to represent different versions. In this case, a user profile document could include an "versions" field that contains an array of embedded documents, where each embedded document represents a different version with its own set of fields. This allows for easier reference within a single document, while also keeping related data together. For instance, you might have a structure like this:

```json
{
 "userId": "123",
 "versions": [
 {
 "version": 1,
 "data": {
 "name": "Alice",
 "email": "alice@example.com"
 },
 "timestamp": "2023-01-01T12:00:00Z"
 },
 {
 "version": 2,
 "data": {
 "name": "Alice Smith",
 "email": "alice.smith@example.com"
 },
 "timestamp": "2023-02-01T12:00:00Z"
 }
 ]
}
```

In addition to these strategies, it's essential to consider selecting a method for resolving conflicts when multiple updates occur simultaneously. One approach is to implement a write lock, where a document can only be updated by one process at a time. Alternatively, you might use optimistic concurrency control, where each update checks for the most recent version of a document before applying changes. By doing this, you can ensure data integrity and maintain a clear history of changes, enhancing the overall robustness of your application.