Question about using multiple recognizers with same model and different grammar

Hi Team,
I am using Vosk api for continous speech recognition in an android application. The offline ASR works very well and by supplying grammar word list the recognition has very high accuracy.
Currently, I want to let the app accept more complicated voice command from user. For example, when user first speak "open file", then I will ask him to provide the file name. In the second phase, I need to recognize the file name from his voice input. However, since all possible filenames is dynamically loaded from db, I will need to start a new recognizer (with the file names as grammar) and speechService.
So my question is whether dynamically construct multiple short-term used recognizer and speechservice be expensive on resource. Or will that cause problem if I have several recognizer/services created in memory and switch between them based on application context?
Thank you for any suggestion.
Regards,
Steven