I built an email alert for my users (now are only 2,000) so every night a crontab execute a php script that query the mysql to find matches with user's saved search. it's a classified website in my case, but i would like to learn in case i had to build something for bigger clients

benim endişeleri vardır:

1. what happen if my user grow x10 or x100 times? is the server going to crash? there any tip you can suggest on manage something like that?

2. there is any way to protect my file cron/nightly_script.php to be executed form outside calling it in the url of the browser? consider tham im using a string in crontab like:

   vaşak [mutlak url / script.php]

3. what about the email blast? for each query if the query has results the script sends an email, so it means a blast of emails...is it going to be considered spam automatically and then i could blacklisted?

teşekkürler!