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Timestamps versus booleans

Using timestamps in place of booleans: exploring the tradeoffs

As a developer, one of the challenges you face regularly is deciding which data type to use in your database. While the choice often depends on the specifics of the project and its requirements, it is essential to weigh the advantages and disadvantages of each option. In this video, we'll explore using timestamps instead of booleans and the tradeoffs that come with them.

To better illustrate this, let's consider an example where we'll create a table named "posts." This table will have several columns, but for demonstration, we'll focus on the "is_archived" column, which indicates whether a post has been archived.

title VARCHAR(125),
-- ....
is_archived BOOLEAN

Initially, we set the "is_archived" column as boolean, which is a useful data type. It allows us to store a true/false value in a single bit, providing an optimal storage solution for storing binary values. However, using timestamps instead of booleans has its benefits too.

Benefit of using timestamps instead of booleans

When we change the data type to timestamps, we get access to an extra piece of information. Instead of just storing a boolean value, we get to store an archive timestamp, which tells us when the post was archived.

title VARCHAR(125),
-- ....
archived_at timestamp null

With this in place, we can still use the archived_at column as if it is a boolean value with the following query:

SELECT * FROM posts WHERE archived_at IS NULL;

This query returns all unarchived posts, which is equivalent to the boolean query

SELECT * FROM posts WHERE is_archived = false;

However, the archived_at column provides us with more information, namely the time at which the post was archived, which could be useful in the long run.

The tradeoffs of using timestamps

While using timestamps provides us with extra information, it has a few tradeoffs that we must consider.

A timestamp column uses four times more storage space than a boolean column, which uses only one byte. As a result, when using timestamps, we need to be mindful of the amount of storage space we use. In a large database, the extra space usage can be significant but it usually doesn't make too much of a difference.

If we decide to put an index on the is_archived column, it is unlikely to be selective enough to benefit the query. Most posts won't be archived, so querying for posts that aren't archived will not use the index. This is another reason why using a slightly larger column doesn't matter that much, as it's unlikely to be indexed.


As a developer, it is always essential to understand the available options and make informed decisions based on the project's specific requirements. Ultimately, it depends on the project's specific requirements and the tradeoffs you're willing to accept.

About this lesson

When storing a boolean value, it's sometimes nice to know when that specific boolean was turned on. Using a timestamp as a boolean can accomplish both of those purposes in one column.

Closed captioned

Meet your instructor, Aaron Francis

Developer Educator at PlanetScale

I’m a dad to one-year-old twins and a software developer with a keen interest in processes and automation.

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