具有20,000,000条记录的MySQL表是否可以快速并发访问？

I ran a lookup test against an indexed MySQL table containing 20,000,000 records, and according to my results, it takes 0.004 seconds to retrieve a record given an id--even when joining against another table containing 4,000 records. This was on a 3GHz dual-core machine, with only one user (me) accessing the database. Writes were also fast, as this table took under ten minutes to create all 20,000,000 records.I ran a lookup test against an indexed MySQL ta