[Phpwm] Multiple MySQL insert techniques

[pete graham]

Good afternoon developers,

I would like your advice. I have a website which has an internal
messaging system for users. The site admins have the ability to send
out a message to all users on the site.

The site has around 6,000 users currently and uses a MySQL Database.
The admin messages go into a admin_messages table. They then get
inserted into the messages table when a user logins into the site (the
separate messages table is required as we need to record is a user has
read messages).

We now want to send an email notification when the admin sends a
message. I'm concerned if I trigger 6,000 mysql inserts when an admin
sends a message it will flood the DB connection. Am I being paranoid
or could this kill the site/DB?

Here are the solutions I've been considering:
 - set up a cron job to batch insert the data into the messages tables
 - use some form of clever sub query to insert the multiple items
(could this also risk killing the db?)
 - leave the message insert logic as it is and modify the batch email
sending to work from a join on admin_messages with the users table

I'm open to other suggestions, if anybody has them. I predict the user
base of the site could grow to around 20,000 users.

Thanks,
Pete