Why do we use multiple database connections?

Why do we use multiple database connections? What is the primary use of this?

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If your application wants to work with two (or more) databases, it will have to use multiple connections.

Another reason might be to run several operations in parallel (for example, handle several user requests in a web application). A connection pool is often used in this scenario.

Are these the cases you wanted to discuss, or is there something else you had on your mind?

Compare a database connection to a cash register in a super market. If there is only one, everybody has to line up at that one single cash register to pay for their shopping. Imagine how long this line could become if there are several dozens of people wanting to pay.

So just like there often are multiple cash registers to help multiple people at once (thereby splitting the single long line into multiple shorter ones), multiple database connections allow more requests to be handled at once. In any web application this is really a must, otherwise your website could only service one user at a time.