Syntax:
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
(https://dev.mysql.com/doc/mysql-errors/8.0/en/server-error-reference.html
#error_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.

URL: https://dev.mysql.com/doc/refman/8.0/en/insert-delayed.html

