Principal Application Engineer Interview Questions and Answers

To design an application that loads UI fast with many components worked on by multiple teams, focus on optimizing code, utilizing lazy loading, implementing caching mechanisms, and conducting regular performance testing.

• Optimize code by reducing unnecessary dependencies and minimizing the use of heavy libraries

• Implement lazy loading to only load components when they are needed, reducing initial load time

• Utilize caching mechanisms to store frequently accessed data locally, red...read more

Retrieve data from two tables using SQL JOIN to combine related records.

• Use INNER JOIN to get records that have matching values in both tables.

• Example: SELECT * FROM TableA INNER JOIN TableB ON TableA.id = TableB.a_id;

• Use LEFT JOIN to get all records from the first table and matched records from the second.

• Example: SELECT * FROM TableA LEFT JOIN TableB ON TableA.id = TableB.a_id;

• Use RIGHT JOIN to get all records from the second table and matched records from the first.

• Example...read more

Implementing multiple API calls concurrently using asynchronous programming techniques

• Use asynchronous programming techniques such as Promises or async/await in JavaScript to make multiple API calls concurrently

• Create an array of Promises for each API call and use Promise.all() to wait for all calls to finish

• Consider using libraries like Axios or Fetch for making API calls in a more efficient manner

useEffect is a React hook used for handling side effects in functional components.

• useEffect is used to perform side effects in function components, such as data fetching, subscriptions, or manually changing the DOM.

• It runs after every render by default, but you can specify dependencies to control when it runs.

• It can return a cleanup function to clean up any resources created by the effect.

• Example: useEffect(() => { fetchData(); }, [dependency]);

Design an LRU cache to efficiently manage data retrieval and storage using a least recently used eviction policy.

• Use a hash map for O(1) access to cache items.

• Implement a doubly linked list to maintain the order of usage.

• On cache hit, move the accessed item to the front of the list.

• On cache miss, add the new item to the front and evict the least recently used item from the back.

• Example: If cache size is 2 and items are accessed in order 1, 2, 1, 3, the cache will contain 1 an...read more