Collection ID length in MongoDB

Question

i am new to mongodb and stack overflow.

I want to know why on mongodb collection ID is of 24 hex characters? what is importance of that?

Answer 1

Now mongoDB current version is 4.2. ObjectId size is still 12 bytes but consist of 3 parts.

ObjectIds are small, likely unique, fast to generate, and ordered. ObjectId values are 12 bytes in length, consisting of:

• a 4-byte timestamp value, representing the ObjectId’s creation, measured in seconds since the Unix epoch

• a 5-byte random value

• a 3-byte incrementing counter, initialized to a random value

Create ObjectId and get timestamp from it

> x = ObjectId()
ObjectId("5fdedb7c25ab1352eef88f60")
> x.getTimestamp()
ISODate("2020-12-20T05:05:00Z")

Reference

Read MongoDB official doc