High Write Count/sec in my RDS server

Recently we have encountered seriously problem since we moved our mysql database from EC2 to RDS. We do have high cpu usage before moved to rds, but our website has a good speed for our customers. After set up instance in RDS, our speed dramatically down without any reasons. We checked our metrics on RDS, then we found that we have almost 100 write count/sec in anytime of day, even we do not have too many customers at nighttime, but the write count/sec is still remain around 100 count/sec. And we have checked our general_log and slow_log files, but we do not where the write operations from ? Anyone experience similar problems ? Our configuration of rds: Mysql 5.6.23 db.r3.large **Our metrics snapshot:** Many Thanks