I have an application concept where 50k people or more need to access a database with 500k records. Each person can only access between 10 and 30 records from this DB. This has to be done once every 4 weeks or so. User should not be able to access the contents of the database besides the 10 or 20 records they can have access to. What is the best way of going about doing this? I have thought that maybe the only way would be with Blockchain but this could be very expensive as far as I know, mybe I m wrong. Any suggestions?