Can i Make Index for all columns(No write operations)?
This all depends on the size of the table. You're doing a full table scan without a where clause so an index isn't going to help. The use of the rand() function for sorting is going to produce a temp table and this will harm performance. If you have a primary key you could generate a random number in the app and perform a query where a single row is selected and can make use of the clustered index. You're likely to be serving this all from memory if you're using the InnoDB storage engine.