high concurency issue with read-write on mysql table
Please provide SHOW CREATE TABLE; it is more descriptive than DESCRIBE.

Please show us samples the INSERTs and UPDATEs and SELECTs; we need to talk about the indexes.

Purging 'old' data can be done 'instantly' if you use PARTITION BY RANGE(TO_DAYS(datetime)) ...  See here .

Are most of the fields really NULLable?  Use NOT NULL where appropriate.