You need to search your state law to find how to expunge the arrest record, which is maintained in the law enforcement agency that has jurisdiction over the arrest. Arrest does not mean complaint filing or a conviction. Normally, you can request an expungement directly from the agency. Upon finding that factually you are innocent the agency will, upon consent of the DA office, seal the record. This is rare and such a request will usually be denied. Future employers may or may not have access to such a record. If they found it, they would inquire and you need to show whatever document you got from the police or a court to explain.