Amazon Android Engineer Interview

So, let's talk about the HR interview at Amazon – that initial step in the software engineer interview journey. Once your resume catches their eye, you'll get a call from an Amazon recruiter or HR for a 30-minute chat.

This interview is your chance to showcase your personality, interests, and skills relevant to the role. Expect the usual HR interview vibe – they want to know more about you and figure out if you're a good fit for the gig.

Now, here's the real deal: Amazon is all about those leadership principles. So, during this HR interview and pretty much every other stage, they'll be watching to see if you vibe with their principles. Our advice? Get acquainted with Amazon's leadership principles—and you're halfway there. Every time you talk about your experiences or skills, tie them back to these principles. 

So, there are three of these online assessments, and they pretty much follow a similar pattern. Whether you're aiming for an entry-level role or something a bit higher up the ladder, you'll be facing these assessments.

For entry-level candidates, each assessment is split into three parts, and you've got a 5-day deadline for each. Here's the interesting part – it doesn't matter how you do in one, you're still getting all three. So, no need to stress about not acing every single part.

Here's what each OA typically covers:

• Online Assessment 1 (Code Debugging): In this OA, you'll encounter a buggy piece of code, and your job is to find the issues and make it run smoothly. 
• Online Assessment 2 (Coding and Workstyles): The second round brings in a mix of coding challenges and something about workstyles. For instance, you might get a coding problem followed by a scenario like how you'd handle conflicting priorities in a project. Or you'd be asked to collaborate with an Android Engineer on a coding exercise. So, in this OQ, you'd not just be proving your coding prowess, but also giving them a glimpse of how you approach work-related scenarios. 
• Online Assessment 3 (SDE Work Simulation): Finally, the third assessment involves a simulation of software development work. You'll be thrown into scenarios that mimic real-world SDE situations at Amazon.

Platforms like LeetCode and HackerRank are your best bets to prepare for these rounds. Mix it up – challenges range from easy to hard, so be ready for anything. Practice under conditions similar to the actual test; set a timer, create a distraction-free environment, and mimic the pressure. This will help you build confidence and adaptability. 

If you make it through the online assessments at Amazon, the next stop is usually the technical phone screen. It's a 45-60 minute rollercoaster of coding challenges, problem-solving, and a deep dive into data structures and algorithms (DSA). Amazon also includes dynamic programming unlike other FAANG companies like Meta. 

Basically, you'll be tackling coding exercises and problem-solving scenarios that test your Android development experience. Make sure you practise coding challenges on platforms like LeetCode or HackerRank. Focus on common algorithms (sort, search) and data structures (arrays, linked lists, trees). Also, brush up on system design concepts and be ready to discuss trade-offs in your design choices. 

Again, don't forget about the Amazon Leadership Principles – make sure you've got some stories up your sleeve that showcase your leadership prowess.

For the main on-site round, you're looking at around 4-5 rounds, and each of these is going to be roughly an hour long. About 4 of these rounds will dive deep into your coding skills, covering everything from data structures & algorithms to computer science fundamentals and system design. You'll be expected to tackle these coding challenges on a whiteboard. You might also find the Meta Android Engineer and Tinder iOS Engineer guides useful.

In addition to this, there's the "Bar Raiser" round. This one's a behavioural interview that revolves around Amazon Leadership Principles. Each one of your interviews has a dedicated 15-20 minutes focusing on the bar raiser, while the remaining 35-40 minutes is allocated to the actual round.

Among the most challenging of all these is the system design round (Android); let's discuss this in detail.

Android System Design Round

The Android system design interview is essentially about proving your ability to build a scalable system. It’s more of a straightforward discussion on the basics — how different components fit together, explaining why you'd choose one approach over another, and general concepts. It goes on for about 45 minutes and doesn't include any coding challenges.

Understandably, communication skills are key here. They'll be looking to you to explain your thought process clearly—your design choices, how you balance trade offs, etc. 

The questions you might face cover a range from simple tasks like fetching data and displaying a list to more complex scenarios like building an IoT or real-time chat app. Though, truth be told, those super complex systems aren't something most candidates run into often.

Here's 5 key areas you typically need to cover:

• You need a solid grasp of architecture patterns like MVC, MVP, MVVM (including nuances like Android Databinding vs Jetpack ViewModel). Additionally, be well-versed in tools such as Dagger-2, RxAndroid, Retrofit, OkHttp, Room ORM, SQLite-db, Hilt, and adhere strongly to SOLID design principles.
• Show them that you know basic Android parts like Activities, Views, Fragments, and Services. Also, use your experience to explain how more advanced parts might work. And design everything that happens on the phone. Make sure to factor in phone limitations like battery, bandwidth usage, and storage. Explain how you'd handle tasks happening in the background
• Don't forget the typical Android OS stack on devices – kernel, hardware abstraction layers, system servers, apps, the usual suspects.
• Lastly, try to get some interview-like practice and insights into what it's really like to interview for this round. You can seek help from an Android engineer at Amazon; they can provide valuable guidance and even provide feedback to help refine your answers. You can connect with an Android Engineer at Amazon via Prepfully here—book a practice session directly.

Bar Raiser Interviews (Behavioral Round)

In Amazon on-site interviews, there's this round called the Bar Raiser Interview, and it's a bit different. You'll interview with a bar raiser who isn't a part of your team; their job is to figure out if you're a good fit for Amazon based on leadership qualities and how well you vibe with their company culture.

Expect some usual technical questions, but the focus is more on your behaviour and how you'd fit into Amazon's way of doing things. So, get ready to share stories that highlight your leadership skills and show you're on the same wavelength as Amazon's culture.

Interview Questions:

• Design Instagram
• Design TikTok
• Design Twitter
• Design Uber
• Design WhatsApp
• Discussion and design of an LRU cache
• Design a garbage collection system
• Design a system to capture unique addresses worldwide
• Design a recommendation system for products
• Design a toll system for highways
• Design a URL Shortener
• Design an Instant Messenger
• Design an Elevator system
• Design a distributed caching system
• Design Amazon Locker Service
• Design Amazon Best Seller Item Service
• What is a red-black tree? Describe a situation where you would use one. Present a solution on the whiteboard to a problem involving a red-black tree.
• Create a system capable of running background services.
• Given two strings that represent numbers, sum the two numbers and return the result as a string. (e.g., "12" + "13" -> "25").
• Reverse a string.
• Implement a function to check if a given string is a palindrome. Optimize for time and space complexity.
• How would you design a system to track inventory levels for an e-commerce platform?
• Implement a binary search tree and write a function to find the kth smallest element.