Twilio Interviews

Hi Folks, I recently completed Twilio’s interview process for the Software Developer (L1) position. The process began when a Twilio recruiter contacted me via LinkedIn about the opportunity. The following day, I had a recruiter screening call over Zoom, where we discussed my current work experience, and the recruiter provided details about the role and the interview process.

Interview Process

Round 1: Coding/DSA This round involved two questions that I had to solve in 45 minutes. The first problem was to find duplicates in an array, and the second was to reorder a linked list.

Round 2: System Design (HLD) For this round, I was asked to design an audit system for e-commerce platforms, with a focus on the data aspect. By the end of the interview, I was able to present a complete and functional design. Additionally, the interviewer asked a scenario-based question related to Twilio’s MAGIC values, assessing my alignment with the company’s core principles.

After successfully clearing both rounds, I was invited to the final hiring manager round.

Round 3: Hiring Manager The conversation started with introductions and a discussion of my current experience, followed by some behavioral and scenario-based questions. I found the hiring manager very approachable and easy to talk to.

Result: Selected Overall, Twilio’s interview process was smooth and transparent, with clear communication throughout. I had a great experience interviewing with Twilio, and I'm pleased to share that I was selected for the position.

https://leetcode.com/problems/stock-price-fluctuation/description/ - implement rest api around this problem to support CRUD operations. Each datapoint will have stockCode, timestamp, price. 1) POST -> store the data point for the give stock and timestamp. 2) PUT -> Update the price for the given stock and timestamp. 3) DELETE -> Delete the price point of the given stock and timestamp. 4) GET -> latest, minimun, maximum stockPrice for the given stock. timestamp is unique in any given stock.

I recently had the opportunity to interview at Twilio, which was quite an exciting prospect for me. As a fresher with an M.Tech degree from a Tier 1 college, this was an on-campus opportunity. The interview process was structured into four consecutive 45-minute rounds: two coding rounds, followed by a system design round, and finally a managerial round.

For both coding rounds, the interviewers provided a HackerRank link containing problems that were unique and not commonly found in standard LeetCode sheets, though they were of medium difficulty. The expectation was to pass all test cases. My experience in these rounds was positive; the interviewers were friendly and even offered hints when I struggled to pass all test cases in the second round, discussing my approach and providing guidance.

The system design round was distinct. Instead of typical large-scale system designs, I was given a single table schema and tasked with designing a complete database from it. This required me to demonstrate my understanding of core database concepts such as normalization (1NF, 2NF, 3NF), table dependencies, and primary keys. The emphasis was on clearly explaining my thought process and the reasoning behind each design decision I made to ensure efficient data storage and manageability, without needing to write any SQL code.

Finally, the managerial round focused on evaluating my experience and behavioral consistency. I was asked about my previous internship experiences and how I handled various professional scenarios. Specific questions included how I would assist a teammate who struggles with clear communication and how I resolved a conflict with a team lead during an internship. I found it crucial to take a moment to gather my thoughts before responding to ensure consistency and thoughtfulness in my answers.

The interview process at Twilio began with an initial online test. After successfully clearing this assessment, I was invited for subsequent remote interviews. The complete process was structured to include 3-4 rounds, but I only participated in two before receiving a rejection.

Round 1: Coding Challenge
I was presented with a problem involving pairs of numbers, where my task was to find the maximum overlapping intervals among these pairs. Additionally, I needed to identify the top 'n' overlapping intervals from the given set. Unfortunately, I was unable to complete the code for this problem within the allotted time, which was a significant factor in my rejection.

Round 2: Database Design
This round focused on database design, which I found to be relatively straightforward. The key steps involved identifying the main entities, defining primary keys and foreign keys to establish relationships between the tables, and then illustrating the 'happy flow' using an Entity-Relationship (ER) diagram.

Ultimately, I was rejected from the process because I could not finish my code for the Round 1 problem.

I applied for an L2 position at Twilio in Bangalore through LinkedIn, and a recruiter reached out to me shortly after. My background includes a B.Tech degree from a Tier 3 college and approximately 1.5 years of experience at a product-based SaaS company. The entire interview process took around 1 to 1.5 months due to interviewers being in different time zones, leading to weekly or bi-weekly scheduling.

Hackerrank Coding Round (1.5 hours)

This was a remote round where a dedicated machine was provided for all tasks. Although I can't share specific details due to an NDA, I can generalize the types of problems encountered:

1. One task involved creating and hosting a web server for an application. I was given the desired output and had the flexibility to use any tools, with Nginx/Apache suggested for the web server and NodeJS/Python for the application. It was a simple application, focusing on testing my knowledge and applicable tools.
2. Another task required performing some mathematical operations using an Infrastructure as Code (IaC) tool.
3. Both solutions had to be executable with a single command, producing sequential output in the terminal, suggesting the use of a bash function or custom script.
4. There was also a coding question of easy-to-medium difficulty, related to string manipulation and regular expressions.

The recruiter followed up with positive feedback, and my onsite rounds were scheduled for the subsequent weeks.

Onsite Interviews (each round 45-60 minutes)

Round 1 (Senior Engineering Manager - Screening)

This round began with an introduction to my current team and work. The questions were primarily focused on my current role, responsibilities, and some specific to Twilio's magic values. We discussed what DevOps is and its importance, as well as the backend tools and frameworks I've utilized. There were several "tell me about a time" behavioral questions related to my work, leadership, and responsibility. I also had questions about my learning techniques and patterns, such as how I would approach learning a new technology or framework within a given timeframe.

Round 2 (Senior Engineering Manager - Design)

After an introduction, I was asked to pick a major project from my experience and discuss its High-Level Design (HLD) and Low-Level Design (LLD). I explained it diagrammatically, detailing each component and data flow. We covered the problem my project solved, its scale, the challenges I faced, and how I overcame them. I also had to justify the choice of tools, languages, and frameworks, discussing potential alternatives and the impact created by the project.

Round 3 (Senior Product Manager - Bar Raiser)

I hadn't specifically prepared for bar raiser questions, but fortunately, they were all relatable to my current work. The interviewer gave a brief introduction before diving straight into "tell me about a time" scenarios:

• ...when I had a feature request from a customer and how I implemented it differently from the expected flow.
• ...when I had to coordinate with multiple teams to complete a task on time and push it to production.
• ...when I took initiative and brought impact to my team, detailing the results.
• ...when I experienced a failure in delivering a task or an issue in production after deployment.
• ...if given a new product team, how I would scale, improve, and set processes to level up the team.
• I also discussed my most recent manager review and how I improved based on the feedback.
• Finally, I talked about a large-scale project I worked on, including its challenges, impact, problem statement, and effects.

Round 4 (Engineering Manager - Hiring Manager)

This round started with very descriptive and lengthy introductions from both sides. The hiring manager explained his team and my potential responsibilities, as well as the expectations for the role. We delved into the steps and processes involved in starting a new product within a company, requiring an end-to-end detailed flow covering product building, market knowledge, POC, internal implementation, beta launch, and public release. Although the interviewer asked for a high-level overview, he delved deeply into each topic. We also discussed a time I worked on a large-scale project and how we brought it to completion, my journey into tech, what motivates me, and all the technical things I've worked on, including personal projects. Lastly, I was asked about how I learn any new technical topic from scratch.

Round 5 (Senior Developer - Coding/Low-Level Design)

After introductions, we moved to a design question focusing on backend infrastructure: how would I design a backend for a website application to handle concurrent user requests and scale effectively? The key requirements were no performance degradation, zero downtime during deploys and upgrades, fault tolerance, rollback support, and CI/CD integration. I gathered that the interviewer was looking for a microservices architecture leveraging Kubernetes and Docker. Beyond this main design problem, I was also asked about various Docker instructions in a Dockerfile, how to tag a Docker image using automation (looking for specific tools and logic), the complete flow of a request from an application connecting to internal servers (including components like ALB/ELB, Route53 DNS, Redis, Firewall, Nginx, proxies, CDN), and strategies for deploying a new application version to production without downtime. Finally, I had to explain how to automate building new Docker image versions and applying them to the respective applications.

Round 6 (HR Round)

This was the final round where the verdict and interview feedback were shared. We then proceeded to salary negotiation and compensation breakdown discussions.

Overall, the process was thorough and well-structured, culminating in an offer from Twilio.