Lesson 3 — The Data Lifecycle: Collect, Store, Retain, Delete

Retention schedule

A documented list of how long each record type is kept.

Crypto-shredding

Destroying the key so encrypted data can never be read again.

SAR

Subject Access Request — a person asking for a copy of their data.

Right to erasure

The right to have personal data deleted in certain circumstances.

Shadow copy

An unmanaged duplicate of data (export, backup, log, laptop file).

A user signs up, then two years later asks to be deleted. Where does their email actually live?

1. 1Production DB: users table — easy to delete.
2. 2Analytics: Event pipeline stored the email as a user property — needs a deletion API call.
3. 3Email provider: The marketing tool holds a contact record — must be purged too.
4. 4Logs & backups: Server logs and nightly snapshots contain it — apply log retention limits and crypto-shredding.

sql-- Delete support tickets closed more than 2 years ago
DELETE FROM support_tickets
WHERE status = 'closed'
  AND closed_at < now() - interval '2 years';

-- Anonymise old orders instead of deleting (tax law needs the totals)
UPDATE orders
SET customer_email = NULL,
    customer_name  = 'REDACTED',
    ship_address   = NULL
WHERE created_at < now() - interval '7 years';

Sometimes you must keep the record for law but remove the personal parts — that is anonymising for retention.