Interview Email Subscription Reminder

Description

What's going on here? So... These scripts are designed to send notifications to users about their expiring subscriptions. It alerts users one and three days before their subscription ends with the message "{username}, your subscription is expiring soon". Detailed information about the task can be found on TASK.md.

Important Notes

• >5 000 000 * 0.2 * 0.85 >= 850 000 - these are completely approximate numbers of unconfirmed emails with a subscription.
• Since email verification is a paid service, it is economical to verify only those emails that are associated with an active subscription.
• The check_email script can take up to 1 minute to verify an email (60 * 24 = 1 440 per day in worst case), which could become a bottleneck.
• Considering the above, checking before sending email is not an option at all. It is better to move the verification into a separate job.
• Tables contain basic indexes and are not expanded due to possible low fields selectivity, so they should be expanded with a better understanding of the real db cases.
• Function lock_process is used to prevent duplicate runs.

Running the Service

1. Ensure that PHP and Composer are installed on your system.
2. Run composer install to install all dependencies.
3. Set up the database using schema.sql.
4. Define the necessary cron jobs in scheduler.cron.
5. To start the service, execute the scripts located in the /scripts directory.