Honestly, other software programs have managed to include this type of functionality with no speed detriment. Generally speaking, If someone reaches the point where they cannot enhance an application further without constant fear of performance penalties, then it's time to look at coding practices and the language it's programmed in. I don't believe that's the case here, though.
I agree. The operation of checking to see if a record exists in a file is a relatively quick process. Of course there are always interactions with the operating system, hard disk and third party programs like virus checkers and malware programs to consider as contributers to performance issues.
I do believe that Esword is ripe for refinement in a few areas. I'm sure Rick has things in mind and is working from a list of program enhancements as well as some modules that may help defray the costs of operation.