Mysql composite index, followed

The table is used to save the 10000 collection information devices sent by the device. it will be added in the future. one collection information and one monthly table will be sent every 5 seconds. there will be tens of millions of records: the order of the device Id and collection time in the index, which is the first and which is the last, mysql index

The table is used to save the collection information sent by the device.
The number of devices is tentatively set to 10000, which will be increased in the future. one collection information, one monthly table, and ten million records will be sent every 5S.
Problem:
The order of the device Id and collection time in the index,