Data Modelling, Constraints and Integrity for Secure Systems

IntermediateFree5 modules · 15 lessons · ~2 min

About this course

Data modelling treated as a security control rather than a design aesthetic. You will cover normalisation to the point it actually helps, primary keys, foreign keys and check constraints as the last line of correctness, and nullability and cascade chains that decide how far a mistake or a deletion actually reaches. The course closes with soft deletes and the retention problems they create, and the three common tenancy models with the specific way each one's isolation actually fails.

What you'll learn

Why Data Modelling Is a Security Control, Not Just a Design Choice

Modelling Decisions That Prevent Whole Classes of Bug
Normalisation: How Far Is Far Enough
Over-Normalising: When Correctness Work Becomes Its Own Risk

Keys and Constraints as the Last Line of Correctness

Primary Keys, Uniqueness and Why 'the Application Enforces It' Is Not Enough
Foreign Keys and Referential Integrity: ON DELETE and ON UPDATE Behaviour
Check Constraints and Not-Null: Encoding Business Rules at the Data Layer

Nullability and Referential Integrity Decisions

Nullability: What NULL Actually Means and Why Ambiguity Is a Security Problem
Cascades: When ON DELETE CASCADE Helps and When It Silently Destroys Data
Orphaned Rows, Dangling References and the Cost of Skipping Foreign Keys

01Why Data Modelling Is a Security Control, Not Just a Design Choice3 lessons

Modelling Decisions That Prevent Whole Classes of Bug
Normalisation: How Far Is Far Enough
Over-Normalising: When Correctness Work Becomes Its Own Risk

02Keys and Constraints as the Last Line of Correctness3 lessons

Common questions

How much does Safeguard Academy cost?

Nothing. Every course, exam, and certificate on the catalog is free — including retakes. All you need is a free Safeguard account.

What are the prerequisites?

None. The flagship course, Safeguard Certified Practitioner, is a beginner-level course — basic familiarity with how software is built helps, but every exam question is answerable from the lessons themselves.

Soft Deletes and the Retention Problem They Create

Soft Deletes: Why Teams Reach for Them and What They Actually Cost
The Query-Filter Risk: Forgetting WHERE deleted_at IS NULL
Soft Deletes Versus Right to Erasure: Reconciling Retention Obligations

Tenancy Models and Their Isolation Implications

Three Tenancy Models: Shared Table, Schema-per-Tenant, Database-per-Tenant
Isolation Failure Modes: Cross-Tenant Leakage in Each Model
Choosing and Evidencing a Tenancy Model: A Decision Table

Primary Keys, Uniqueness and Why 'the Application Enforces It' Is Not Enough

Foreign Keys and Referential Integrity: ON DELETE and ON UPDATE Behaviour

Check Constraints and Not-Null: Encoding Business Rules at the Data Layer

03Nullability and Referential Integrity Decisions3 lessons

Nullability: What NULL Actually Means and Why Ambiguity Is a Security Problem
Cascades: When ON DELETE CASCADE Helps and When It Silently Destroys Data
Orphaned Rows, Dangling References and the Cost of Skipping Foreign Keys

04Soft Deletes and the Retention Problem They Create3 lessons

Soft Deletes: Why Teams Reach for Them and What They Actually Cost
The Query-Filter Risk: Forgetting WHERE deleted_at IS NULL
Soft Deletes Versus Right to Erasure: Reconciling Retention Obligations

05Tenancy Models and Their Isolation Implications3 lessons

Three Tenancy Models: Shared Table, Schema-per-Tenant, Database-per-Tenant
Isolation Failure Modes: Cross-Tenant Leakage in Each Model
Choosing and Evidencing a Tenancy Model: A Decision Table2 min

What happens if I fail the exam?

You can retake it after a 24-hour cooldown, as many times as you need. Retakes are free, and each attempt draws a fresh random set of questions.

How long is a certificate valid?

The Safeguard Certified Practitioner credential is valid for 24 months from issue. The expiry date is printed on the certificate and shown live on its public verification page. Renewing means passing the current exam again.