# Versioned MySQL Replica ## Problem * Is your production MySQL vulnerable to data loss? * If an operator runs a bad query, script, or deployment can your production MySQL can be down for hours or days as you recover data from backups or logs? * Are you worried your backups aren't working? * Does internal audit want an immutable log of what changes on your MySQL instance? * Do you want the ability to copy and sync your production MySQL database for analytics, development, or debugging? ## Dolt solves this by… Because Dolt is [MySQL-compatible](/sql-reference/benchmarks/correctness.md), you can set Dolt up as [a versioned replica](/introduction/getting-started/versioned-mysql-replica.md) of your MySQL primary. Every transaction commit on your primary becomes a [Dolt commit](/concepts/dolt/git/commits.md) on the Dolt replica. On your Dolt replica, you get a full, immutable, queryable audit log of every cell in your database. If an auditor wants guarantees that a cell in your database has not been modified, you can use Dolt to prove it. [Diffs](/concepts/dolt/git/diff.md) can be produced for every transaction. If an operator makes a bad query, runs a bad script, or makes a bad deployment, you have an additional tool beyond backups and logs to restore production data. Find the bad transactions using Dolt's audit capabilities. Rollback the bad individual transactions. [Produce a SQL patch](/sql-reference/version-control/dolt-sql-functions.md#dolt_patch) and apply that back to your primary. If there are conflicting writes, Dolt will surface those for you and you can decide how to proceed. A Dolt replica becomes an essential part of your disaster recovery plan, shortening some outages by hours or days or recovering lost production data. Moreover, Dolt can be added to your serving path as a read-only MySQL replica, so you know that it is always in sync with your primary. Your disaster recovery instance can serve production traffic so you always know it's working. Additionally, a Dolt replica can be easily cloned (ie. copied) to a developer's machine for debugging purposes. See a data issue in production? Debug locally on your laptop safely. ## Dolt replaces... ### Backups and Transaction Logs Dolt as a versioned replica becomes your first line of defense against a bad operator query, script, or deployment. Dolt is online and contains the full history of your database. In a disaster you can use diffs to find a bad query and roll it back. Then you can produce a database patch and apply it to production. You do not need to reinstall from a backup and play the transaction log back to the point of the failure, an extremely time consuming process. ### Change Data Capture [Change Data Capture](https://www.dolthub.com/blog/2023-03-01-change-data-capture/) is a way to add a history of data changes to an existing database. Modern change data capture tools consume replication logs to produce database changes in a consumable stream. Dolt can consume the same logs producing a simpler change data capture solution. ## Companies Doing this * [NoCD](https://www.treatmyocd.com/) ## Case Studies Let us know if you would like us to feature your use of Dolt as a versioned MySQL replica here. ## Related Articles * [Dolt Binlog Replication Preview](https://www.dolthub.com/blog/2023-02-17-binlog-replication-preview/) * [Getting Started: Versioned MySQL Replica](https://www.dolthub.com/blog/2023-03-15-getting-started-versioned-mysql-replica/) * [Versioned MySQL Replicas on Hosted Dolt](https://www.dolthub.com/blog/2023-04-05-versioned-mysql-replicas-on-hosted-dolt/) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.dolthub.com/introduction/use-cases/versioned-replica.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.