Web-Based Evaluation, synonymous with 'Online Assessment' conducted on platforms like Hackerrank or Codility, is an initial protocol that candidates need to pass to secure a Software Development Engineer role at Amazon. The performance in this online evaluation decides if the applicant's profile is suitable to proceed to telephonic or in-person (alternatively, virtual) interviews.
Amazon OA1, OA2, OA3
You may have heard of the terms OA1, OA2, or even OA3. What this means is part 1, part 2, and part 3 of the online assessment. OA1 is debugging questions and OA2 is LeetCode-style coding questions. Sometimes there is also an OA3 which is a work style assessment with no coding.
If you are an experienced SDE you will likely only be required to pass one of them, the OA2. If you are interviewing for an Amazon SDE intern or new grad position, you will be required to write OA1 and OA2 and maybe OA3.
Amazon OA1
OA1 involves debugging and logical reasoning. For debugging, you will be given a short code with a subtle error and asked to fix the error. The common errors include incorrect loop conditions causing an infinite loop and off-by-one errors, etc. Typically, there are 5-7 debugging questions. There may also be logic and reasoning questions or simple math questions. For example, given a sequence like this 4 12 6 18 12 36 30, what should the next number be? The answer is 90 because you may notice the numbers in the even positions are 3x the numbers in the previous odd-positioned number.
Amazon OA2
OA2 is the LeetCode style coding questions. You will be given one to two questions to solve in 1.5 hours. See the list below for practice.
Amazon OA3
OA3 is work style assessment and logic reasoning. For work style assessment, you will be put in a hypothetical situation and required to take the most “Amazonian” action. Be sure to review the 14 leadership principles and use them to guide your choices.
Amazon Online Assessment Practice
| Practice question | Pattern |
|---|---|
| Robot Bounded in Box | Math logic |
| Number Game | Bitmask |
| Find All Combination of Numbers Sum to Target / Shopping Options | DFS |
| Fill the Truck | Basic coding/greedy |
| Slowest key | Basic coding |
| Binary Tree Level Order Traversal | BFS |
| Longest Substring without Repeating Characters | Two Pointers |
| Five Star Seller | Priority Queue/Heap |
| Subarray Sum Divisible by K | Prefix Sum |
| Merge Two Sorted Lists | Priority Queue/Heap |
| LRU Cache Misses | Data Structure Design |
| Music Pairs | Two Pointers |
| Minimum Difficulty of a Job Schedule | Dynamic programming |
| Autoscaling Policy/Utilization Checks | Two Pointers |
| Optimal Utilization | Two Pointers |
| Minimum Total Container Size | Dynamic programming |
| Shopping Patterns | Graph |
| Amazon Prime Air Route | Two Pointers |
| Move The Obstacle | Graph BFS |
| K Closest Points | Priority Queue/Heap |
| Number of Swaps to Sort / Algorithm Swap | Divide and Conquer |
| Reorder Data in Log Files/Upgrading Junction Boxes | Basic coding |
| Top K keywords | Priority Queue/Heap |
Core Patterns Asked in Amazon Online Assessment and Virtual Onsite Interviews
Almost all Amazon questions can be solved using one of the following patterns.
- Two Pointers
- Breadth-first Search
- Depth-first Search
- Backtracking
- Heap and Priority Queue
Each pattern is divided into a number of sub-patterns. We have introduction articles and practice problems for each of sub-pattern. Make sure you know them well before going into the interview.
You may also need to know a little bit of dynamic programming but just the basics like coin change and house robber.
More frequently asked questions about Amazon OA:
Does Amazon online assessment use webcam?
At the beginning of the OA, you will be asked to take a picture of your ID using the webcam. But the actual OA test is not recorded by the webcam.
Is Amazon online assessment timed?
Yes. The time may vary depending on the platform. On HackerRank it's typically 135 min.
Is Amazon SDE online assessment proctored?
There is no human to proctor the assessment, but you will be asked to take a picture of your ID at the beginning of the test and your browser activity is monitored. So don't switch tabs too frequently - it may get picked up as a signal for looking up things on Google.
Can you Google during Amazon online assessment?
Your browser activity is monitored. So be sure to get familiar with the syntax and common data structures of your language of choice.
How is Amazon online assessment evaluated?
Your solutions will be tested against open and hidden test cases and the results will be used to decide whether you move to the next round of interview.
How hard is Amazon online assessment?
It depends on your luck. It could range from leetcode easy to hard. But most of the questions are not too difficult. See the list above to get a sense of difficulty and practice the corresponding patterns.
How to prepare for Amazon online test?
Use the list above and AlgoMonster's Amazon patterns to prepare.
What happens after Amazon online assessment?
You will hear back from the recruiter in a few days. If you are looking for an intern role, you will be given multiple OAs and then the "virtual onsite" interview (commonly referred to as the VO). If you are an experienced engineer, you will go onto the (possible virtual) onsite interview directly.
How do I pass the OA and VO?
If you have your test next week, go close all your other browser windows right now and practice the problems above. If you have a bit more time, the highest return-on-investment thing you can do in your tech career is to master the patterns. Then you can solve almost any problem. We highly recommend you to practice the patterns and follow the AlgoMonster system.
 (2024))
