Business Logic
What rule must hold even when someone bypasses the interface, repeats a request, or receives an external-service error? Express important rules once in a testable backend boundary rather than scattering them across screens and integrations.
What You Will Be Able to Decide
- Explain business logic in product and business terms.
- Apply this decision: Express important rules once in a testable backend boundary rather than scattering them across screens and integrations.
- Recognise this material risk: different entry points apply different versions of the same commercial rule.
- Use this review: Trace one support request from submission to stored status, including a duplicate click and a provider timeout.
A founder is reviewing how the product will enforce rules and respond when a request does not go to plan. This lesson gives you a concrete question to take into a build brief, proposal review, or product decision.
What rule must hold even when someone bypasses the interface, repeats a request, or receives an external-service error? The course example is A service that lets customers submit and track support requests; use it to decide what evidence would justify the choice before a builder implements it.
What Does Business Logic Mean for Your Product?
A founder is reviewing how the product will enforce rules and respond when a request does not go to plan.
Use the illustrative service for this course (A service that lets customers submit and track support requests) to make the choice concrete. What rule must hold even when someone bypasses the interface, repeats a request, or receives an external-service error?
Technical term
Business Logic
Business logic is the set of product-specific rules that decides what may happen, in what order, and with what consequence.
How Should a Founder Use Business Logic?
For a service that lets customers submit and track support requests, ask what would happen if different entry points apply different versions of the same commercial rule.
For this decision, the useful standard is that important rules hold for valid, invalid, repeated, and unauthorised requests.
- Decision: Express important rules once in a testable backend boundary rather than scattering them across screens and integrations.
- Evidence to request: show that important rules hold for valid, invalid, repeated, and unauthorised requests.
- Owner: name who will respond if different entry points apply different versions of the same commercial rule.
- Record the result in the backend proposal and operational acceptance criteria.
- Practical review: Trace one support request from submission to stored status, including a duplicate click and a provider timeout.
How Do You Choose an Approach to Business Logic?
What rule must hold even when someone bypasses the interface, repeats a request, or receives an external-service error? Express important rules once in a testable backend boundary rather than scattering them across screens and integrations.
The risk is that different entry points apply different versions of the same commercial rule. Compare a simpler option with the proposed one, including who will operate either choice.
- Describe the user or business outcome that must be protected.
- Identify the most credible failure and its consequence.
- Compare the simplest adequate approach with one realistic alternative.
- Set a review point for when the decision may need to change.
What Evidence Should You Accept for Business Logic?
What Warning Signs Should You Look For?
- The proposal does not address this risk: different entry points apply different versions of the same commercial rule.
- Nobody can show whether important rules hold for valid, invalid, repeated, and unauthorised requests.
- The decision has no named owner or review point.
What Should You Ask a Consultant?
- What changes for the user if we choose this approach to business logic?
- How have we reduced or accepted this risk: different entry points apply different versions of the same commercial rule.
- Can you demonstrate that important rules hold for valid, invalid, repeated, and unauthorised requests?
- Who owns the result, and when will we reconsider it?
Key takeaway
Key Takeaway
Express important rules once in a testable backend boundary rather than scattering them across screens and integrations. Ask for evidence against the specific risk: different entry points apply different versions of the same commercial rule.