FAANG Interview Questions Experienced

Top 30+ FAANG Interview Questions Experienced Candidates Must Know

The FAANG Interview Questions Experienced are designed to assess your problem-solving ability, coding proficiency, and system design expertise at a higher level. These questions typically cover complex algorithms, data structures, design patterns, and behavioral skills essential for success at top-tier tech companies like Facebook, Amazon, Apple, Netflix, and Google.

This collection of over 30 recent and frequently asked FAANG Interview Questions Experienced candidates should prepare for will strengthen your technical knowledge and help you approach interviews confidently.

1. Explain the difference between a balanced and an unbalanced binary tree.

A balanced binary tree maintains a height difference of at most one between left and right subtrees at every node, ensuring O(log n) time operations, whereas an unbalanced tree can degrade to O(n).

2. How do you detect a cycle in a directed graph?

By using Depth-First Search (DFS) with a recursion stack or by applying Kahn’s algorithm for topological sorting.

3. Write code to find the median of two sorted arrays.

def findMedianSortedArrays(nums1, nums2):
    A, B = nums1, nums2

    # Ensure A is the smaller array
    if len(A) > len(B):
        A, B = B, A

    total = len(A) + len(B)
    half = total // 2
    l, r = 0, len(A) - 1

    while True:
        i = (l + r) // 2  # A's cut index
        j = half - i - 2  # B's cut index

        Aleft = A[i] if i >= 0 else float('-inf')
        Aright = A[i + 1] if (i + 1) < len(A) else float('inf')
        Bleft = B[j] if j >= 0 else float('-inf')
        Bright = B[j + 1] if (j + 1) < len(B) else float('inf')

        # Valid partition
        if Aleft <= Bright and Bleft <= Aright:
            if total % 2:
                return min(Aright, Bright)
            return (max(Aleft, Bleft) + min(Aright, Bright)) / 2
        elif Aleft > Bright:
            r = i - 1
        else:
            l = i + 1

print(findMedianSortedArrays([1, 3], [2]))       # Output: 2
print(findMedianSortedArrays([1, 2], [3, 4]))    # Output: 2.5

4. What is the time complexity of quicksort in the best, average, and worst cases?

Best and average case time complexity is O(n log n), while worst case is O(n²) when the pivot is poorly chosen.

5. Describe the CAP theorem.

CAP theorem states that a distributed system can only simultaneously guarantee two out of three: Consistency, Availability, and Partition Tolerance.

6. How would you design a URL shortening service like bit.ly?

I would focus on scalability, unique key generation, data storage (NoSQL for fast lookups), API endpoints for creating and retrieving URLs, caching, and analytics.

7. Explain the difference between process and thread.

A process is an independent execution unit with its own memory space, while threads are smaller units of execution within a process that share the same memory.

8. What is dynamic programming and when is it used?

Dynamic programming breaks problems into overlapping subproblems and stores results to avoid redundant computations, commonly used in optimization problems.

9. Write a function to detect if a linked list has a cycle.

def hasCycle(head):
    slow = fast = head
    while fast and fast.next:
        slow = slow.next
        fast = fast.next.next
        if slow == fast:
            return True
    return False

10. What are different ways to handle concurrency in programming?

Common ways include using locks, semaphores, mutexes, atomic operations, and concurrent data structures.

11. Explain the concept of memoization.

Memoization stores the results of expensive function calls and returns cached results when the same inputs occur again.

12. What is the difference between a deadlock and livelock?

Deadlock is when processes wait indefinitely for resources held by each other, while livelock is when processes continuously change states without progress.

13. How do you find the lowest common ancestor in a binary tree?

Recursively check if nodes match or belong in left/right subtrees; the node where both sides return non-null is the lowest common ancestor.

14. Describe the difference between SQL and NoSQL databases.

SQL databases are relational and schema-based; NoSQL databases are non-relational, schema-flexible, and designed for scalability.

15. How would you design a messaging queue system?

Focus on durability, message ordering, fault tolerance, scalability, and support for multiple consumers and producers.

16. Write code to implement a thread-safe singleton in Python.

import threading

class Singleton:
    _instance = None
    _lock = threading.Lock()

    def __new__(cls, *args, **kwargs):
        if not cls._instance:
            with cls._lock:
                if not cls._instance:
                    cls._instance = super().__new__(cls)
        return cls._instance

17. What is garbage collection and how does it work in Java?

Garbage collection automatically frees memory by removing objects no longer referenced; Java uses generational GC with young, old, and permanent generations.

18. Explain the difference between REST and GraphQL APIs.

REST uses fixed endpoints and returns fixed data sets; GraphQL allows clients to specify exactly what data they want via queries.

19. What is the purpose of CAP theorem in distributed systems?

It guides trade-offs between consistency, availability, and partition tolerance when designing distributed systems.

20. How do you implement rate limiting for APIs?

Techniques include token buckets, leaky buckets, fixed windows, or sliding windows to limit requests per user/time interval.

21. Write a function to implement a LRU cache.

from collections import OrderedDict

class LRUCache:
    def __init__(self, capacity: int):
        self.cache = OrderedDict()
        self.capacity = capacity

    def get(self, key: int) -> int:
        if key not in self.cache:
            return -1
        self.cache.move_to_end(key)  # mark as recently used
        return self.cache[key]

    def put(self, key: int, value: int) -> None:
        if key in self.cache:
            self.cache.move_to_end(key)  # update usage
        self.cache[key] = value
        if len(self.cache) > self.capacity:
            self.cache.popitem(last=False)  # remove least recently used

22. How do you detect and fix memory leaks?

Use profiling tools to detect leaks, analyze object references, and fix by removing unnecessary references or closing resources.

23. What is sharding and how is it used in databases?

Sharding partitions data horizontally across multiple machines to improve scalability and performance.

24. Describe your approach to solving coding problems under time pressure.

I break down the problem, clarify requirements, outline a solution, write clean code, and test with sample cases iteratively.

25. Explain how garbage collection pauses can affect performance.

Garbage collection can cause application pauses that impact latency; optimizing GC algorithms and tuning heap sizes reduces impact.

26. Write a function to find the longest substring without repeating characters.

def lengthOfLongestSubstring(s):
    char_map = {}
    left = max_length = 0

    for right, char in enumerate(s):
        if char in char_map and char_map[char] >= left:
            left = char_map[char] + 1  # move left to avoid duplicate
        char_map[char] = right
        max_length = max(max_length, right - left + 1)

    return max_length

print(lengthOfLongestSubstring("abcabcbb"))  # Output: 3 ("abc")

27. What strategies do you use for system design interviews?

I clarify requirements, define system components, discuss trade-offs, sketch high-level architecture, and explain scalability and reliability plans.

28. What is eventual consistency?

Eventual consistency ensures that, given enough time without updates, all nodes in a distributed system will converge to the same state.

29. How do you prevent SQL injection attacks?

Use parameterized queries/prepared statements, validate inputs, and employ ORM frameworks to prevent injection vulnerabilities.

30. Explain the concept of microservices architecture.

Microservices architecture breaks applications into small, loosely coupled services that communicate over APIs, enabling independent development and deployment.

31. How do you optimize database queries?

Use indexing, analyze query execution plans, avoid SELECT *, and denormalize tables if necessary.

32. What are the key differences between synchronous and asynchronous programming?

Synchronous programming waits for each operation to complete before proceeding, whereas asynchronous allows operations to run concurrently, improving responsiveness.

Preparing for FAANG Interview Questions Experienced requires dedication and practice. Focus on understanding concepts deeply and coding efficiently. Use these questions to hone your skills and increase your chances of success in top tech companies. Good luck!