Explain "Tell, Don't Ask" principle.

0-2 years experience

1. 1You have a User class with getAge() and a service that checks age to grant premium access. How would you refactor this to follow Tell, Don't Ask?
2. 2A Cart object exposes getItems() and a function iterates over the items to compute total price. What change would you make to avoid the function asking the cart for its internal list?
3. 3If code does if (order.getStatus() == Status.SHIPPED) { … }, how could you rewrite it respecting Tell, Don't Ask?

2-5 years experience

1. 1Our order processing module calls order.getTotalAmount() then applies discounts in a separate utility, and it broke when new discount rules needed line‑item details. How would you redesign the interaction using Tell, Don't Ask?
2. 2During a code review you see a UserProfile object being passed around and many places call profile.getEmail() to send notifications. What are the trade‑offs of moving the notification logic into UserProfile?
3. 3Feature toggles are scattered as config.isFeatureEnabled() checks across services, leading to inconsistent behavior. How would you apply Tell, Don't Ask to centralize this decision?

5-8 years experience

1. 1Our payment microservice receives a PaymentRequest DTO and multiple handlers query request.getAmount(), request.getCurrency() for validation, logging, and routing. At scale this is a maintenance headache. How would you restructure the component to respect Tell, Don't Ask, and what impact does it have on performance and testability?
2. 2In a large e‑commerce platform, the inventory system frequently asks a Product object for its stockLevel and then decides whether to allocate stock, causing race conditions. How would you redesign responsibility distribution using Tell, Don't Ask, and what concurrency considerations arise?
3. 3A reporting service pulls data from a ReportBuilder by calling many getters to assemble the final report. Explain how you would refactor this so the builder tells the service what to do, and discuss the effect on extensibility.

8+ years experience

1. 1Our monolithic order management system heavily uses 'ask' patterns, exposing internal state across bounded contexts. How would you lead a migration to a microservice architecture that enforces Tell, Don't Ask at the architectural level, and what challenges do you expect with legacy data and cross‑team contracts?
2. 2A cross‑team initiative wants to standardize business object APIs, but some teams argue getters are needed for flexibility. As a staff engineer, how would you convince them of the long‑term benefits of Tell, Don't Ask, and what metrics would you use to measure success?
3. 3Design a policy for API contracts between services that enforces Tell, Don't Ask while allowing versioned extensions. Discuss how this impacts backward compatibility and deployment pipelines.