Race condition

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Definition

A fault where the outcome depends on the timing of two or more processes using the same data, so results are unpredictable (for example two users buying the last ticket).

Example: 'Two withdrawals read the same balance at once.' Prevent with locking.

Found in: syllabus, 2025 HSC marking guidelines, sample exam and familiarisation guidelines, school notes.

Short version to memorise (key terms bank)

Outcome depends on the timing of concurrent access to shared data.

Where you'll use it in the test

Syllabus area: Y12 Secure Software Architecture.

Question types it can appear in

Multiple choice: 2025 Q8 answer: Race conditions
Short answer: Give an example and outline (sample Q22b)

Where it has appeared in the paper

Secure Software Architecture (Part A, B). Part letters follow each paper’s own layout.

How to use it

A model sentence

General advice, built from the definition and example above

“A fault where the outcome depends on the timing of two or more processes using the same data, so results are unpredictable (for example two users buying the last ticket).” Then apply it: 'Two withdrawals read the same balance at once.' Prevent with locking.

In a short answer, give the definition in your own words first, then tie it to the situation in the question. Do not copy the example above unless it fits the scenario.

Command words used with it

From the linked past questions

Identify: Recognise and name. (2025 HSC Q8 (1 mark): User action controls)

Official worked answer

Sample exam Q22b (3 marks): Race conditions (3 marks): official criteria and sample answer

Criteria

3: Provides an example of when a race condition may occur AND outlines how secure code could prevent it. 2: Outlines some features of race conditions. 1: Some relevant information.

Sample answer

With multiple teachers potentially accessing the database at the same time, race conditions can allow malicious users to gain unauthorised access. Authentication could be used to restrict access to the database, and code can be written to use atomic transactions and database locks to time the reading and writing of data.

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Go deeper

Flashcard: Race condition in Secure Software Architecture (Year 12) · study that set
Memorise: User action controls: broken authentication, XSS, CSRF, forwarding, race conditions
Key terms bank entry: Race condition
Master answer: sample-q22b (3 marks, short answer (example + outline, max 75 words)) (Master model answers: Secure Software Architecture)
Notes: User action controls: broken authentication, XSS, CSRF, forwarding, race conditions (Secure Software Architecture (Year 12))
Notes: Design, develop and implement secure code to minimise vulnerabilities in user action… (Secure Software Architecture (Year 12))
Full term page: every question, note and marking comment for Race condition

Check yourself

Explain “Race condition” in one sentence, give an example, and name a question type that could test it.

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