Insert response time in Memory Tables

[Chooi Ting Goon]

I am having inconsistent insert response time in my application. It take 1-2 ms to complete the insert query during beginning of the program when there is less data in the table. When it run for a long time, it takes about 300ms to complete an insert statement. We have other module who will access the table(select), update and delete the records. Question is how can I fine tune MysQL server parameters in order to shortern the insert response time ? If I were to fine tune MySQL parameter on memory table, the parameter involve will be max_heap_table_size and tmp_table_size ??