How does WhatsApp handle the deletion of phone number data upon account deletion from a technical perspective?

[muskanhossain]

When a user initiates account deletion on WhatsApp, the platform undertakes a multi-stage process to remove their data, including their phone number, from its systems. From a technical perspective, this involves several key operations across different database layers and storage mechanisms:

1. Marking the Account for Deletion:

The first step is to logically mark the user's account as "to be deleted" in the primary user database. This might involve updating a status field associated with the user's phone number record.
This logical deletion immediately restricts access to the account. The israel whatsapp number data user will no longer be able to log in, and other users may no longer see their profile or interact with them.
2. Deletion from Primary Databases:

Subsequently, the process moves to physically deleting the user's phone number and associated account information from the active primary databases. This involves executing DELETE commands in the relevant database tables where user profiles, settings, and registration details are stored, using the phone number as the primary key or a key associated with the account ID.
This deletion needs to be carefully managed to ensure data consistency across the distributed database infrastructure that WhatsApp likely employs. Techniques like distributed transactions or eventual consistency models might be used to handle the deletion across multiple shards or nodes.
3. Removal from Linked Data Structures:

Phone numbers are not only stored in the primary user profile but are also likely indexed and linked in various other data structures to facilitate features like contact discovery, group memberships, and message routing.
The deletion process must also identify and remove the user's phone number (or its hashed representation) from these secondary indexes and related data structures to ensure the user is no longer discoverable or associated with these features. This might involve updating or deleting entries in inverted indexes, graph databases (for social connections), and other specialized data stores.
4. Deletion of Associated Content:

While the focus is on the phone number, the account deletion process also triggers the removal of other associated content, such as profile photos, "About" information, and potentially the linkage to message history. While WhatsApp states that messages are typically stored locally on users' devices and not permanently on their servers once delivered, the association between the account (identified by the phone number) and any server-side metadata related to those messages needs to be severed.
5. Handling Backups:

WhatsApp's data deletion policy mentions that even after the initial deletion process, copies of user information may still exist in their backup storage for a certain period (e.g., up to 90 days) for disaster recovery purposes.
From a technical standpoint, these backups are typically point-in-time snapshots of the databases. The deleted phone number and associated data will eventually be overwritten or aged out as new backups are created. Access to these backups is usually restricted to specific recovery processes and not for regular data retrieval.
6. Log Data and Anonymization:

WhatsApp may retain certain log data related to account activity and deletion for analytical and security purposes. However, their policy suggests that this data is disassociated from directly identifying information, including the phone number, through anonymization or pseudonymization techniques over time.
7. Asynchronous Processing:

Given the scale of WhatsApp's operations, the entire deletion process is likely handled asynchronously through a queue-based system. When a user requests deletion, a task is added to a queue, and worker processes handle the various deletion steps in the background to avoid impacting the real-time performance of the platform.
In summary, the technical process of deleting a phone number upon account deletion from WhatsApp involves a logical marking, physical deletion from primary databases, removal from linked data structures, handling of associated content and backups, and eventual anonymization of log data. This multi-stage, asynchronous process is designed to remove the user's identifier and associated information from WhatsApp's systems while ensuring data consistency and minimizing impact on the platform's performance.