MySQL table data in Memory for read operation

It sounds odd but we have table which contain millions rows of data, and we are running query with JOIN, AND, ORDER BY etc operation, because of that Query running slow, Query scanning full table and finding best match result, currently single query taking 2 to 3 second which is not acceptable :(

Can i load full table in Memory and do read operation their? We are not writing data in table so we don't care about lost of data on power off we can quick load table in memory again if need.

I have tried all customization etc. using mysqltunner but didn't help.

Do you guy suggest loading table in Memory will help in read operation?

Other solution we have is sqlite put file on memory and run query on it.