What are slots?

0-2 years experience

1. 1We have a simple page that needs a header and footer shared across multiple pages. How would you use a Slot in a layout to achieve this?
2. 2If you place a <Slot /> inside a layout but the child page doesn't render anything, what will the user see?

2-5 years experience

1. 1You added a Slot to a layout, but the content from a nested page is not showing up. Walk me through how you'd debug this.
2. 2When you need to conditionally render different child components inside the same layout, how can you use multiple Slots or named slots, and what trade‑offs does that involve?

5-8 years experience

1. 1Consider a large e‑commerce site using the app router with deep nested layouts. How would you design the slot hierarchy to minimize server‑side rendering overhead and avoid unnecessary data fetching?
2. 2If a slot renders a server component that fetches data, but a sibling slot renders a client component that also needs the same data, how would you coordinate data fetching to avoid duplicate requests?

8+ years experience

1. 1Your organization is migrating a legacy pages/ directory to the new app directory. What strategy would you use to replace existing layout patterns with Slot‑based layouts while ensuring minimal disruption across multiple teams?
2. 2Discuss the long‑term maintenance implications of over‑using slots for fine‑grained composition in a micro‑frontend architecture. How would you set guidelines to balance flexibility and performance?