How to optimize `select count(1)`?

The count(1) statement counts the total number of rows in a table. Improving the degree of concurrency can significantly improve the speed. To modify the concurrency, refer to the tidb_distsql_scan_concurrency document. But it also depends on the CPU and I/O resources. TiDB accesses TiKV in every query. When the amount of data is small, all MySQL is in memory, and TiDB needs to conduct a network access.