Data Load using Data sync from a service backed record ? design/architecture question

Hi,

Thanks for your help in advance & much appreciated if someone has faced this design scenario already . Bit of background , We have a significant number of historical cases in a DB as we are decommissioning an outdated system . In a nut shell, These cases are not going to change or case count is not going to increase.

case count is significant (10,000 or a million) & number of end users not too much ( around 100 ). We have a REST Api which exposes the DB (containing historical cases) mentioned earlier.

I am creating a site to display this historical case data . I am planning to use record sync to load the data in to a record.

1. As data is not going to change or increase, all I need is data load to the record, not really data sync , Can I still use Appian's record "data sync" facility?
2. Do the "data sync" needs to be run daily ? or I can just load the data once and query the record to filter for example if the data remains static ?
3. This is the interface which is powered by the above service based record . if record sync is not used, I need an api call to fetch each filter call . and to minimise the api calls , I am forced to use a button (SEARCH). Otherwise , if the record is already synced and has the data , I can use normal record filtering and display the filtered result as the user enters each filter field and dont need a search button .I prefer the record sync approach. is this design correct ? I have never worked with record syncs before . is there something I missed ? will there be any issue in the future ? Will record sync affect other applications in the same Appian cloud (performance wise) ?  We have more significant applications in the server , viewing historical cases is not the significant if considered as a whole.