What is Purging & DB Cleanup?

Purging refers to the process of permanently removing outdated, unnecessary, or expired data from the database.

Database Cleanup involves both removing and reorganizing the data to ensure optimal performance. This includes tasks like de-indexing unused fields, archiving old records, and deleting obsolete entries.

In a platform like BookMyShow, where users continuously book tickets, check showtimes, and interact with movie data, purging and cleanup are essential to ensure fast query performance and prevent the database from becoming bloated.

Why is Purging & Cleanup Needed?

• Data Redundancy: The database accumulates data like past bookings, old user details, and outdated movie information. Over time, this data becomes unnecessary.

• Improved Performance: Removing outdated records helps in reducing the load on the database, leading to faster queries and responses. Large datasets can slow down read operations (like searching for a movie or viewing a showtime).

• Cost Efficiency: Storing unnecessary data can increase storage costs. Purging old data helps reduce storage expenses, especially if you’re using cloud services.

• Regulatory Compliance: In some cases, such as GDPR, there might be regulations on how long personal data can be retained. Purging expired or irrelevant data ensures compliance with legal requirements.

• Data Integrity: Over time, orphaned or inconsistent data can exist in the system (e.g., bookings associated with deleted accounts). Regular cleanup ensures that the database remains consistent and accurate.

What Data to Purge & Clean?

In BookMyShow, there are several types of data that might require purging or cleanup:

• Expired Bookings: Tickets for shows that have already passed should be removed. This prevents the database from storing irrelevant booking data and keeps records updated.

• Cancelled Bookings: Users might cancel their bookings, and these records should be updated or deleted from the system to avoid cluttering the database.

• Old Movie Listings: Once a movie’s showtime has passed or the movie is no longer in theaters, old movie listings should be archived or removed to prevent unnecessary records from remaining.

• User Data: Some users may delete their accounts or stop using the platform. Purging inactive user data is important, especially in compliance with privacy laws.

• Logs and Temporary Data: The system may generate logs for debugging or auditing purposes. These logs should be cleaned up periodically to avoid consuming excessive storage.

• Payment Information: For compliance reasons, any payment information that is outdated or no longer required must be removed.

Purging Strategies

There are several strategies BookMyShow can use to handle purging and database cleanup efficiently:

Time-based Expiry:

• For bookings, you can set a retention period (e.g., 30 days after the show date) after which the booking records are automatically purged.
• Logs generated for troubleshooting can also have an expiry period (e.g., kept for 6 months) before they are deleted.

Event-driven Cleanup:

• Purging can occur when certain events happen, such as a movie being removed from the schedule or a user deleting their account.

Batch Purging:

• Rather than purging records one at a time, which could cause performance issues, use batch processing to delete or archive records during off-peak hours (e.g., nightly cleanup jobs).

Archiving Old Data:

• Instead of permanently deleting old records, they can be archived to separate storage (cold storage) or moved to a separate database. This allows for long-term storage without affecting system performance.

Soft Deletion:

• Instead of removing data permanently, a “soft delete” flag can be set on records (e.g., marking them as “inactive”). These records are not included in regular queries but can be purged later in a cleanup cycle.

Database Optimization (Reorganization):

• Periodically, the database may need to be reindexed or defragmented to ensure optimal query performance after significant purging of data.

Challenges with Purging & Cleanup

• Consistency: Ensuring that no related data (e.g., booking records, payment information) is left orphaned after deletion.

• Real-time Performance: Running cleanup tasks in real-time can affect the performance of the system. Therefore, most cleanup tasks should be scheduled during off-peak hours.

• Data Retention Policies: Adhering to data retention regulations can be tricky, especially when it comes to compliance with data privacy laws such as GDPR.

• Data Dependencies: Some data might be interdependent, and purging one piece of data could cause issues in others. For example, deleting a user’s booking might have implications for the theater’s schedule.

How BookMyShow Can Implement Purging & Cleanup?

• Automated Scheduled Jobs: Set up automated jobs that run at regular intervals (e.g., every night) to purge outdated bookings, remove past showtimes, and clean up inactive user accounts.

• Archiving System: Move old records to secondary databases or data warehouses for long-term storage instead of removing them entirely. This can be useful for historical analysis or compliance needs.

• Event-based Triggers: When a movie’s showtimes expire, or when a user cancels a booking, trigger an automatic cleanup to remove or update the relevant records.

• Database Sharding/Partitioning: For large databases, implement sharding or partitioning based on time (e.g., by month or year). This helps manage the cleanup process by making it easier to purge old partitions without affecting current data.

Tools for Purging & Cleanup

Database Management Tools:

• Use tools like MySQL’s Event Scheduler or PostgreSQL’s pg_cron to schedule periodic tasks for cleanup.

Batch Processing Frameworks:

• Systems like Apache Spark or Apache Flink can handle large-scale data cleanup tasks and archiving, especially for logs or large transactional records.

Cloud Storage:

• For archiving purposes, AWS S3, Google Cloud Storage, or Azure Blob Storage can be used to store archived data at a lower cost.

Best Practices for Purging & DB Cleanup in BookMyShow

• Database Backup: Always backup the database before performing large-scale purging or cleanup. This ensures data recovery in case of accidental deletions.

• Implement Logging: Keep logs of all purging and cleanup activities, so if something goes wrong, you have an audit trail for debugging.

• Test Cleanup Jobs: Before running a cleanup job in production, thoroughly test it in a staging environment to ensure that no important data is lost.

• Monitor System Performance: After implementing purging and cleanup, monitor system performance to ensure that the tasks do not negatively impact the system’s responsiveness.