---
title: Database Deployments with Reduced Downtime
description: Making database changes to a running application can be tricky, here are a few things to keep in mind that should reduce or eliminate downtime.
date: 2022-06-27
tags: Database, deployments
source: https://brianchildress.co/blog/database-deployments-with-reduced-downtime
---

# Database Deployments with Reduced Downtime

Once your application or service is running in production you have a lot more to consider when making database changes. It can be tricky, here are a few things to keep in mind that should reduce or eliminate downtime.

## Renaming Columns

If you need to rename a column, to reduce downtime you cannot do the rename all in one release. Let's say that we want to rename `firstName` to `first_name` in our _users_ table. Assuming there is already data in that column in our database we need to take a 3 step approach to complete the renaming process.

Steps:
1. Create a new `first_name` column (keeping the old `firstName` column)
2. Ensure application is writing to **both** columns. Perform a backfill, copying values from the old `firstName` column to the new `first_name` column
3. Cleanup. Once all data has been copied (may require several runs of the backfill), update application to only write to new `first_name` column. Delete old `firstName` column.

## Adding Columns

If you're adding columns, start with updating the database with the new column. If you intend for the new column to not allow for `NULL` values you will need to ensure a default value is supplied when creating the column. After the database has been updated then we can deploy new application or service code to use the new column.

## Removing Columns

If you need to remove a column we need to configure application or service code to no longer use the old column. Once we deploy our code changes then we can remove the old column.