It appears that you were charged if you were given a ticket or a summons and had to appear in court. Either the DA gave you a deferred or dismissed the case outright with you taking the class and writing the essay. I would run a background check to see if it shows up. In all likelihood, it still will and you will need to take steps to file a motion to seal it.
Generally speaking, what ends up showing on a criminal history is not convictions necessarily, but often arrests. Once a person is arrested, a number of outcomes are possible, and many times they do not lead to convictions.
A commercial search will often hit on these arrests. What you must do to prevent this from happening is to "seal" your file. This processes involves opening another civil case to ask a court to order all the criminal justice files to be sealed from the public. If you can get a judge to order that, your file will no longer be visible to members of the general public and the court will deny their existence upon a request.
You can either do this on your own or with the help of an attorney.
The proceeding statement is for your benefit and designed to orient you to seek help more completely; it should not be construed as a complete answer to your legal problem or a substitution for legal advice. Only when an attorney has had the opportunity to fully explore the issues of your case can you truly be advised. By reading my statement you should not infer we have created an attorney client relationship.
Mr. Leroi is correct. Run a background check on yourself. If it shows up, then you should petition to have your record sealed.
This answer does not create an attorney-client relationship. It is advisable to consult with an attorney with full disclosure of relevant facts for a comprehensive leagl opinion.