Questions
6 of 14
1What is a slice in Redux Toolkit?
2How is a slice different from a traditional Redux reducer?
3What are the key properties inside createSlice()?
4How does createSlice() automatically generate action creators?
5What does the name field in a slice represent?
6How do you combine multiple slices into one store?
7How do you access a slice’s state in a component using?
8Can you modify the state directly in a slice reducer? Why does it work?
9What’s the purpose of extraReducers in createSlice()?
10How do you handle async actions (e.g., thunks) inside a slice using extraReducers?
11What is the difference between reducers and extraReducers in a slice?
12How do you organize slices in a large application?
13Can multiple slices modify the same part of state?
14How do you reset a slice’s state to its initial value?
RTKRTK
Basics
Slice
Actions
Reducers
RTK Query
Store
Thunk
Scenario Based
06 / 14

How do you combine multiple slices into one store?

In Redux Toolkit, multiple slices can be combined into a single Redux store using the configureStore() function. Each slice manages its own part of the state, and all are added as separate reducers under unique keys.

Steps to Combine Slices
  1. 1

    Create individual slices for different features (e.g., userSlice, counterSlice).

  2. 2

    Import all slice reducers into a central store file.

  3. 3

    Use configureStore() to combine them into one store by passing an object to the reducer field.

  4. 4

    Each slice’s name (or key in the reducer object) determines its section of the global state.

Example: Combining Multiple Slices
Difficulty: 6/10
Topics: createEntityAdapter, combineSlices, reducer composition

Scenario Questions

0-2 years experience
  1. 1

    You have two RTK slices — one for users and one for posts. How would you combine them into a single store so both can be accessed from the same root state?

  2. 2

    If you forget to export the reducer from one of your slices, what happens when you try to combine them with combineReducers? What would you see in the dev tools?

2-5 years experience
  1. 1

    A feature team added a new slice for comments, but now the UI isn’t updating when comments are added — the state changes in Redux DevTools but components don’t re-render. What could be wrong and how would you debug it?

  2. 2

    You’re combining three slices, but one of them keeps resetting to its initial state after a page refresh. What’s likely causing this and how would you fix it?

5-8 years experience
  1. 1

    You’re migrating a legacy Redux app to RTK and need to combine 15+ slices. How would you structure the folder and import system to avoid circular dependencies and keep maintainability?

  2. 2

    One of your combined slices has a high-frequency update (e.g., real-time chat messages). How would you optimize performance to prevent unnecessary re-renders across unrelated UI components?

8+ years experience
  1. 1

    Your company has 5+ teams using RTK slices independently, but now you need to combine them into a single store for a new monolithic dashboard. How would you design a governance model to prevent naming collisions and ensure consistent state shape across teams?

  2. 2

    You’re tasked with migrating a large app from vanilla Redux to RTK with combined slices, but some legacy reducers rely on side effects in action creators. How would you phase this migration without breaking existing features or requiring a big-bang rewrite?

Follow-up Questions

  • ❓What happens if two slices have the same key name?
  • ❓How would you debug a state update that isn't triggering a re-render?
  • ❓Why not just use one big slice instead of combining multiple?