Incremental indexing for an external API call params

Am building an app , so the external API call requires an index +1 when to provide a unique address for a new sign up user . So how do I implement a +1 incremental index in drapcode so that when a new user sign up , it gives him an index +1 even though a +5 deleted his or her account it will consider +6 ?

Am looking forward to more knowledge to path params since the video on path params doesn’t explicitly explain bon different cases