Speaking as a programmer and MySQL DBA, additional connections are a nothing relative to everything else. Period, end of story, don't even worry about it.
Instead, you should be worrying about the following:
- Are your tables properly normalized?
- Are you using all the features provided by your RDBMS to ensure data integrity?
- Are your primary keys database-generated, meaning that your user-facing information can be easily altered? The perfect example of this is using an auto-generated id vs. the username as the primary key for your users table.
Remember - the point of a database has more to do with keeping your precious data secure from the stupid programmers who want to pollute it and less to do with the speed with which you can get answers to questions. If your data is corrupted, then you're going to get very fast answers that are wrong. Start with correctness and add speed later.
My criteria for good software:
- Does it work?
- Can someone else come in, make a change, and be reasonably certain no bugs were introduced?