MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
INSERT DELAYED ...
The DELAYED option for the
INSERT statement is a MySQL
extension to standard SQL. In previous versions of MySQL, it can
be used for certain kinds of tables (such as
MyISAM), such that when a client uses
INSERT DELAYED, it gets an okay
from the server at once, and the row is queued to be inserted
when the table is not in use by any other thread.
DELAYED inserts and replaces were deprecated
in MySQL 5.6. In MySQL 8.0,
DELAYED is not supported. The server
recognizes but ignores the DELAYED keyword,
handles the insert as a nondelayed insert, and generates an
ER_WARN_LEGACY_SYNTAX_CONVERTED
warning: INSERT DELAYED is no longer supported. The
statement was converted to INSERT. The
DELAYED keyword is scheduled for removal in a
future release.