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Category: engineeringblog

June 4, 2025

From DNS Failures to Resilience: How NodeLocal DNSCache Saved the Day, Sanu Satyadarshi

I am Sanu Satyadarshi, part of the Platform Engineering division at Mercari, Inc. Platform Engineering provides a cost-effective, safe, and easy-to-use multi-cloud infrastructure service for all engineering teams to make and scale bets. This article discusses the DNS-related challenges encountered at Mercari on our Kubernetes clusters and the significant improvements achieved by implementing Node-Local DNS Cache. By optimizing DNS traffic and reducing errors, we enhanced system reliability and scalability, preventing production outages caused by DNS failures. Key Takeaways Reduced DNS calls to kube-dns by 10x, decreasing network overhead and inter-service communication costs. Lowered DNS query rates by 93% for services on the cluster. Achieved a 10x-100x reduction in DNS-level errors, improving system resilience. Eliminated the “failed to refresh DNS cache” errors, mitigating a frequent source of incidents. DNS on Kubernetes: The Elephant in the Room Domain Name System, more commonly known as DNS an extremely critical component in the internet infrastructure. This is the tech that allows your web browser to find the actual IP address of a website when you type example.com in your browser. DNS in itself is a highly complex topic, and understanding it requires a book(or two) on its own. Like any network infrastructure, Kubernetes depends on DNS to resolve service names like [service name].[namespace].svc.cluster.local and other names to IPs and allows communications among services and the external world. From the role of DNS in Kubernetes, you can imagine that any DNS failure or degradation can quickly escalate to increased latency, network congestion, and even complete outages. On Kubernetes, DNS is installed as a kube-dns deployment running on the kube-system namespace. Specifically at Mercari, it comes pre-installed with our managed GKE clusters for service discovery and name resolution across the clusters. kube-dns on Kubernetes allows multiple configurations using the configmap that can be used to change various parameters like ndots, etc. As kube-dns is responsible for resolving all… <a class="more-link" href="https://about.in.mercari.com/news/mercari-india/from-dns-failures-to-resilience-how-nodelocal-dnscache-saved-the-day-sanu-satyadarshi/">Continue reading <span class="screen-reader-text">From DNS Failures to Resilience: How NodeLocal DNSCache Saved the Day, Sanu Satyadarshi</span></a>

April 10, 2024

Mentoring the Future: My Experience with Build@Mercari Program

Hello everyone, I’m Sanu Satyadarshi, currently serving as a Lead Software Engineer at Mercari. Recently, I had the privilege of being a mentor for the Build@Mercari 2024 program, and I’m excited to share my experiences from this incredible event. Build@Mercari stands as Mercari Inc.’s premier pre-internship initiative, offering online training and internship opportunities to university students worldwide. This immersive program provides hands-on training, allowing students to dive into the tech stack commonly used in the industry. Selected participants are grouped into teams, with each team being assigned 1-2 mentors. Throughout the program, students undergo comprehensive training covering essential skills such as Git, GoLang/Python, Web API development, Docker, CI/CD, and more. This year, the event commenced on Feb 16, 2024, accommodating both online and offline formats. Online sessions catered to English-speaking students, while offline sessions were tailored for Japanese-speaking students. I had the privilege of mentoring the English-speaking group (while still honing my Japanese language skills 😞). Our initial session focused on assisting students in installing and setting up Git, a fundamental skill for any Software Engineer. Following this, students were divided into smaller groups, with dedicated mentors assigned to each team. The experience was incredibly engaging. We began by configuring our development environments, setting up Golang/Python on our laptops, and deploying a sample web application to showcase the iconic “Hello World!” message on our browsers. As the Build@Mercari sessions emphasize technical proficiency, I volunteered to lead sessions on Docker and CI, in addition to the introductory GoLang session. During the Docker session, I introduced the concept of containers, followed by a demonstration and hands-on exercise on containerizing a GoLang application. Students successfully created containerized applications and executed them on their laptops. In the CI session, we utilized GitHub actions to automate the building of Docker images upon each PR merge, highlighting… <a class="more-link" href="https://about.in.mercari.com/news/engineeringblog/mentoring-the-future-my-experience-with-buildmercari-program/">Continue reading <span class="screen-reader-text">Mentoring the Future: My Experience with Build@Mercari Program</span></a>

April 9, 2024

Swift Innovations Unleashed: A Look Inside the Mercari India Meetup

Hello, I’m Archita Bansal, currently working as a Lead Software Engineer at Mercari India. What an incredible day we had on February 10th at Mercari India! The Swift Meetup transformed into a unique gathering of Swift developers from various backgrounds, making it a special day filled with insights and collaboration. This event was much more than a Mercari India initiative; it was a testament to community collaboration. By welcoming Swift developers from different companies, we fostered an environment rich in shared learning and connections. Our attendees had the chance to engage with top Swift technology experts, including Mercari India’s own speakers and notable external specialists. Together, they navigated a wide array of topics, from optimizing build speeds in both local and CI environments to ensuring applications are accessible through comprehensive accessibility audits. The discussions didn’t stop there—they also covered practical tips for applying SwiftUI in production apps, showcasing the framework’s incredible power and flexibility, and delved into the innovative potential of MapKit in SwiftUI. The evident enthusiasm and passion from each presentation truly highlighted the vibrant spirit of the Swift community. It was a day of innovation, learning, and community building, a sentiment strongly supported by the positive feedback we received across social media. The meetup transcended the bounds of mere technical presentations; it embodied the spirit of collective growth and vision. Guided by our leadership, insights were shared that illuminated the core of iOS development at Mercari, revealing the ambitions and principles that unite us all. Being part of such community events demonstrates Mercari India’s dedication to fostering a culture of innovation and collaboration, reaching beyond our immediate space. Reflecting on the meetup, we’re overwhelmed with gratitude for the moments we shared, the knowledge we exchanged, and the connections we forged. This event was a collaborative effort that benefitted… <a class="more-link" href="https://about.in.mercari.com/news/engineeringblog/swift-innovations-unleashed-a-look-inside-the-mercari-india-meetup/">Continue reading <span class="screen-reader-text">Swift Innovations Unleashed: A Look Inside the Mercari India Meetup</span></a>

January 22, 2024

SWE Intern to an Android Engineer: Unveiling the chapters of my experience at Mercari India

Hello, I’m Mrudul Tora, and I’m thrilled to share the comprehensive journey of becoming one of the Software Engineer Interns at Mercari India, spanning from the initial interview process to securing a Pre-Placement Offer (PPO) and converting to a full time Android Engineer. A closer look at Mercari Mercari Inc., founded in 2013, is a prominent Japanese e-commerce company. The Mercari marketplace app, introduced in Japan in July 2013, has evolved into the country’s largest community-powered marketplace, facilitating over 23 Million active users each month. Application Process Motivated by a previous setback in the application process, I approached this opportunity with renewed determination. I meticulously updated my resume, ensuring it highlighted all relevant projects and internships. Applying through a referral in December 2022, I eagerly awaited the next steps. To my delight, within a few days, I received a link for an online test, marking the beginning of an exciting chapter in my journey with Mercari. First Round: Online Assessment The initial phase involved an online assessment conducted on the HackerRank platform. The assessment comprised three coding-based questions, all centered around data structures and algorithms. Notably, the difficulty level for all the questions was medium. The assessment was to be taken in two weeks, and a duration of one hour was allocated for the test once it was initiated. Taking advantage of the given time span, I dedicated a portion to revisiting and reinforcing my understanding of data structures and algorithms before attempting the test. Following the completion of the assessment, a member from the Talent Acquisition (TA) team reached out to me. This interaction included discussions about my preferred duration and location for pursuing the internship, allowing for a personalized touch to the process, with options between India and Japan. Post-assessment, there was a waiting period of approximately two… <a class="more-link" href="https://about.in.mercari.com/news/engineeringblog/swe-intern-to-an-android-engineer-unveiling-the-chapters-of-my-experience-at-mercari-india/">Continue reading <span class="screen-reader-text">SWE Intern to an Android Engineer: Unveiling the chapters of my experience at Mercari India</span></a>

January 11, 2024

Mercari’s Recruitment Journey at IIT Kharagpur

Hello, I’m Sanu Satyadarshi, currently working as a Lead Software Engineer at Mercari India. Mercari stands as a beacon of tech innovation, consistently upholding rigorous engineering standards. We firmly believe in the infusion of fresh perspectives, and our new graduate hires—often referred to as freshers—play a key role in infusing new ideas and dynamism into our systems. India’s burgeoning tech landscape has become a magnet for companies scouting world-class engineering talent. Recognizing this trend, Mercari has cultivated relationships with top-tier Indian engineering institutions for several years. As part of our annual recruitment strategy, we recently visited the esteemed IIT Kharagpur, a global powerhouse in engineering education. While our hiring process might appear simple, it’s anything but that. Planning commences a minimum of 6–8 months in advance, with our new-grad talent acquisition team meticulously orchestrating every detail. This time around, the hiring was being done for positions in Japan. However, since Mercari has a software development center in India, I was nominated by my manager to visit IIT Kharagpur directly and conduct interviews in support of the hiring team from Japan. At Mercari, we believe in working together toward common goals, and this is just one embodiment of our company value “All for One.” Here’s where the logistics get interesting: I was in Tokyo, Japan, until November 29th, with interviews scheduled in Kharagpur on December 1st. This tight schedule required quick transitions, including flights from Tokyo to Bangalore and then to Kolkata, followed by an early morning drive to Kharagpur. During the morning drive from Kolkata to Kharagpur, I was able to discuss a lot of technical topics with Mercari’s CTO Ken Wakasa, VP of Engineering Carlos Donderis, and other senior engineering leaders who had traveled from Japan for the hiring initiative. Upon reaching IIT Kharagpur, we were accommodated at the… <a class="more-link" href="https://about.in.mercari.com/news/engineeringblog/mercaris-recruitment-journey-at-iit-kharagpur/">Continue reading <span class="screen-reader-text">Mercari’s Recruitment Journey at IIT Kharagpur</span></a>