--- title: "Latest reads" description: "The engineering internet, summarised so you can actually read it." --- # Latest reads > The engineering internet, summarised so you can actually read it. ## Articles ### [Grabbing Growth: A Growth Hacking Story](https://yomu.fyi/post/grabbing-growth-a-growth-hacking-story.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Gaurav Sachdeva - Published: Dec 8, 2017 Grab established a dedicated Growth Hacking team within its Technology organization to pursue high-risk, niche initiatives and scale impact across 68 million regional users. Positioning the team within engineering allowed rapid A/B testing and simultaneous multi-market deployments driven by structured growth loops. The team prioritizes and evaluates all initiatives using a Growth Factor metric, calculated as the increase in rides divided by the increase in costs. To improve driver engagement, the team implemented a Spin-to-Win game based on B.F. Skinner's variable ratio reinforcement principles, delivering probabilistic monetary and merchandise rewards upon meeting daily ride thresholds. Ongoing regional experiments continue to evaluate metrics including driver acceptance, cancellation rates, and driver ratings. ### [The Data and Science Behind GrabShare Part I: Verifying Potential and Developing the Algorithm](https://yomu.fyi/post/the-data-and-science-behind-grabshare-part-i-verifying-potential-and-d.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Tang Muchen - Published: Oct 20, 2017 Expanding from point-to-point dispatch services to dynamic carpooling requires matching independent passenger requests traveling in similar directions without causing unacceptable delays. Grab evaluated the feasibility of its GrabShare service by analyzing historical trip data with DBSCAN clustering on coordinates projected into a Universal Transverse Mercator system. This analysis demonstrated that 35% to 46% of rides across typical daytime windows fell into tight geographic clusters with near-identical pickup and drop-off coordinates. The resulting matching framework adapts the baseline dispatch flow by searching for in-transit drivers and enforcing real-time seat reservation constraints. Route assignment decisions subsequently evaluate detour times, trip angles, and expected arrival times to ensure driver utilization improves while total driving distance decreases. ### [The Art of Hiring Good Engineers](https://yomu.fyi/post/the-art-of-hiring-good-engineers.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Rachel Lee - Published: Oct 4, 2017 Building and scaling engineering teams requires adapting recruitment strategies across different organizational sizes, from initial hires to hundreds of engineers. Teams often begin with small groups of battle-tested engineers before designing formal hiring pipelines. The recruitment approach outlines four key steps: sourcing top-tier talent from platforms like GitHub and LinkedIn, assessing technical fit through tailored screens or assignments, evaluating cross-functional and culture fit via group interviews, and optimizing the process. This optimization includes routing candidates strategically to strict bar-raiser interviewers to prevent burnout and expedite decisions. ### [Migrating Existing Datastores](https://yomu.fyi/post/migrating-existing-datastores.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Nishant Gupta - Published: Aug 8, 2017 Grab's Identity team faced imminent memory exhaustion on a single Redis node used to cache mobile authentication tokens under rapid user growth. Because read traffic outweighed write traffic by roughly 200 times, the team opted for an AWS ElastiCache cluster with three shards and two read replicas per shard. They executed a zero-downtime, six-phase migration plan while handling a peak load of 20,000 queries per second. The migration transitioned through initial one-time data replication, asynchronous shadow writes, synchronous dual writes, asynchronous read validation, switching primary reads, and final write cleanup. Controlled by feature flags and monitored with metrics at every stage, the migration completed without invalidating tokens or causing service disruptions. ### [So You Need to Hire Good Engineers](https://yomu.fyi/post/so-you-need-to-hire-good-engineers.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Rachel Lee - Published: Jul 24, 2017 Hiring strategies in fast-growing technology startups dictate the quality and scalability of expanding engineering teams. Insights gathered from conversations with over one hundred engineering leaders identify crucial evaluation criteria across technical competence, cultural alignment, and problem-solving capability. Candidates rarely present a perfect technical fit, requiring hiring managers to weigh passion, willingness to learn, and risk appetite against baseline technical requirements. Rather than focusing solely on static factual questions, interviewers gain deeper insights by probing the rationale behind candidates' architectural and implementation choices. High-caliber engineers ultimately elevate team capability by simplifying complex challenges, writing cleaner code, and learning quickly. ### [Come and #hackallthethings at Grab](https://yomu.fyi/post/come-and-hackallthethings-at-grab.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Grab Engineering - Published: Jul 11, 2017 Grab has officially launched a public bug bounty program in partnership with HackerOne to strengthen the security of its platform. This rollout follows a private bounty initiative operated over the previous year, during which the organization worked with over 350 security researchers and resolved nearly 200 awarded bug reports. The new public program invites external researchers to scrutinize Grab's code for critical flaws, including remote code execution, SQL injections, and exportable cross-site scripting vulnerabilities. To support ethical and responsible disclosure, Grab offers payouts reaching up to $10,000 per valid vulnerability report based on severity and impact. ### [How We Scaled Our Cache and Got a Good Night's Sleep](https://yomu.fyi/post/how-we-scaled-our-cache-and-got-a-good-night-s-sleep.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Gao Chao - Published: Jun 19, 2017 Growing business load on the Common Data Service (CDS) created potential bottlenecks for its single-threaded Redis cache on ElastiCache, necessitating horizontal scaling for greater capacity and throughput. After ruling out master-slave replication and intermediate Twemproxy setups due to memory constraints and proxy I/O bottlenecks, the team implemented client-side sharding. Using an internal Go package for consistent hashing, CDS instances hash cache keys locally to determine the target shard. The implementation encapsulates hashing inside a thin \`ShardedCache\` wrapper sharing the original cache interface while supporting Ketama and custom hash functions. Deploying via double-writing cron jobs during off-peak hours reduced database read pressure and improved P99 latency. ### [Grab's Front End Study Guide](https://yomu.fyi/post/grab-s-front-end-study-guide.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Yangshun Tay - Published: Jun 3, 2017 Rapid hiring and engineering expansion created a steep learning curve for newcomers and backend engineers unfamiliar with modern web architecture. Grab created an opinionated front-end study guide to help engineers navigate JavaScript tooling, state management, and modern application practices. The guide frames client-side single-page applications as a scalable alternative to traditional server-side rendering, enabling clear client-server separation for multiple client apps hitting the same backend API. It establishes core competencies in ECMAScript 2015 via Babel and explains how component-driven interfaces in React improve maintainability and performance through virtual DOM reconciliation. Ultimately, the resource aims to ramp up developer onboarding and accelerate shipping speeds across web platforms. ### [DNS Resolution in Go and Cgo](https://yomu.fyi/post/dns-resolution-in-go-and-cgo.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Ryan Law - Published: May 24, 2017 Go applications experiencing load balancing issues across AWS Elastic Load Balancer (ELB) nodes trace uneven traffic distribution to IP address sorting defined in RFC 6724. Comparing Go's native DNS resolver with Cgo and glibc's getaddrinfo shows that both initially sort destination addresses using Rule 9 longest matching prefix rules. Disabling IPv6 on the network interface causes C and Cgo resolvers to return IP addresses in randomized order, while the native Go resolver continues deterministic sorting. Examination of net/addrselect.go reveals that Go's native resolver implements only a subset of the RFC rules and omits dynamic source address selection. Achieving permanent parity requires modifying the Go source code directly. ### [Driving Southeast Asia Forward with AWS](https://yomu.fyi/post/driving-southeast-asia-forward-with-aws.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Arul Kumaravel - Published: May 21, 2017 Grab transitioned its transportation platform from a single Ruby on Rails monolith on Amazon EC2 and Amazon RDS MySQL to a microservices architecture hosted on Amazon Web Services. The platform processes multi-petabyte real-time data flows and hundreds of millions of GPS data points to match drivers with passengers and push proactive demand heat maps. Operational efficiency is sustained with fewer than ten full-time infrastructure engineers, supported by AWS managed services. The analytics backend also transitioned from MySQL to Amazon Redshift, eventually moving to an Amazon S3 data lake using Amazon EMR and Presto. These data-driven matching systems improved driver-passenger allocation rates by up to 30%. ### [How to Go from a Quick Idea to an Essential Feature in Four Steps](https://yomu.fyi/post/how-to-go-from-a-quick-idea-to-an-essential-feature-in-four-steps.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Da Huang - Published: May 16, 2017 Grab engineered an in-app messaging platform, GrabChat, to help drivers and passengers coordinate pickups across Southeast Asian markets characterized by weak 2G connectivity and high packet loss. The team developed an in-house TCP messaging architecture consisting of a TCP gateway named Gundam and a message dispatcher named Hermes connected to internal backend services over HTTPS. To protect backend server resources from resend loops during poor connection states, the communication protocol adopts a "server only push once" model that delegates retry handling to the client. Data science evaluations using a pre-trained cancellation prediction model confirmed that GrabChat adoption correlated with reduced booking cancellations. Following early usage feedback, the team further iterated on the feature by introducing pre-written message templates to reduce driver distraction on the road. ### [Troubleshooting Unusual AWS ELB 5XX Error](https://yomu.fyi/post/troubleshooting-unusual-aws-elb-5xx-error.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Dharmarth Shah - Published: May 10, 2017 Grab experienced intermittent HTTP 5XX alerts when its Gothena service sent driver location updates to the Astrolabe service through an AWS Elastic Load Balancer (ELB). CloudWatch metrics revealed that requests were failing to reach healthy backend instances because of an uneven load distribution favoring a single ELB node in one Availability Zone. The team verified that Route 53 was properly using Alias records and ruled out OS-level DNS caching since Linux does not cache DNS queries by default. Connection inspection with netstat across multiple Go services confirmed a heavily skewed distribution of connections toward specific ELB IP addresses. Comparative tests with cURL, tcpdump, Go, Python, and Ruby in an isolated environment demonstrated that Go reused connections across requests while other runtimes opened new connections per request. ### [Scaling Like a Boss with Presto](https://yomu.fyi/post/scaling-like-a-boss-with-presto.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Aneesh Chandra - Published: May 1, 2017 Grab experienced severe performance degradation, long queue times, and connection timeouts on its Amazon Redshift analytics cluster as user concurrency and reporting workloads expanded. Although an initial Amazon S3 data lake decoupled storage from compute, business users required standard SQL interfaces rather than Spark data pipelines. The team deployed Presto clusters on AWS EMR, switching their storage format from AVRO to Parquet to support ANSI SQL querying directly against S3. Utilizing a shared Hive metastore on Amazon RDS allowed Grab to adopt a shared-data multi-cluster architecture that isolated distinct workloads across dedicated compute clusters. This setup enabled rapid cluster scaling, streamlined failover, and matched Redshift performance on partitioned time-range queries. ### [Deep Dive into iOS Automation at Grab - Continuous Delivery](https://yomu.fyi/post/deep-dive-into-ios-automation-at-grab-continuous-delivery.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Sun Xiangxin - Published: Apr 23, 2017 Grab manages continuous delivery for its iOS applications using four build configurations per target: Adhoc QA, Hot Dogfood, Dogfood, and Testflight. The engineering team moved away from Fastlane in favor of custom bash scripts under 100 lines that execute clean builds and archives via xcodebuild. To eliminate manual logins for build execution, Grab developed a server-side Swift application integrating SlackKit and a bot named Iris. Incoming Slack commands are parsed and scheduled onto a serial DispatchQueue to trigger the appropriate build scripts. Deployment and rollback of updates to Iris and its build scripts are handled through Capistrano. ### [Deep Dive into iOS Automation at Grab - Integration Testing](https://yomu.fyi/post/deep-dive-into-ios-automation-at-grab-integration-testing.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Sun Xiangxin - Published: Apr 18, 2017 Grab replaced third-party cloud CI services with an in-house Xcode Server pipeline to run automated iOS integration tests across an expanding engineering team. Instead of performing fresh repository clones on shared cloud instances, Xcode Server pulls code incrementally and mirrors local developer configurations. The team automated testing bots through Ruby scripts and Arcanist hooks tied to Phabricator code reviews, dynamically provisioning bots on diffs and deleting them after merges. This architecture preserves step-by-step UI test execution logs and screenshots for easier failure diagnostics. To maintain stability on on-premises hardware, pre-integration scripts clear application cache states using simctl commands. ### [A Key Expired in Redis, You Won't Believe What Happened Next](https://yomu.fyi/post/a-key-expired-in-redis-you-won-t-believe-what-happened-next.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Karan Kamath - Published: Mar 27, 2017 Grab experienced an issue where its Unicorn API served stale data for up to 45 to 60 minutes despite expected cache invalidation times totaling around 11 minutes. The setup utilized ElastiCache Redis 2.x configured with a single master node for writes and two read-only slaves handling reads. Investigation revealed that in Redis 2.x, slave nodes do not expire keys on their own and only delete them upon receiving an explicit DEL command from the master. Because the master only actively checks and deletes 200 random keys per second, clearing expired keys across roughly 5.6 million cached items mathematically required over 110 hours, resulting in slaves serving expired data. ### [How Grab Hires Engineers in Singapore](https://yomu.fyi/post/how-grab-hires-engineers-in-singapore.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Daniel Tay - Published: Feb 16, 2017 Grab maintains a selective engineering recruitment process in Singapore, with only three to five percent of candidates ultimately receiving an offer. The evaluation pipeline typically spans three to four weeks and includes an initial HR phone screen, an online coding round, and consecutive technical interviews. Recruiters assess candidate capability via public GitHub projects, presentations, and technical blogs rather than traditional CV qualifications alone. The company prioritizes experience in low-latency distributed systems and microservices design alongside strong cultural alignment with peer collaboration. ### [Battling with Tech Giants for the World's Best Talent](https://yomu.fyi/post/battling-with-tech-giants-for-the-world-s-best-talent.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Grab Engineering - Published: Jan 18, 2017 Grab maintains research and development centres across Singapore, Seattle, and Beijing to develop mobility and transaction platforms for Southeast Asia. Engineer Brandon Gao turned down an offer from a major Seattle-based technology corporation to remain at the company due to rapid growth and high engineering impact. During backend infrastructure changes starting in May 2015, Grab transitioned core services from Node.js and Ruby to Golang. A weekend Golang prototype created by Gao evolved into the primary data service linking backend servers to 580,000 drivers across the region. Additionally, his initial work on the User Trust team established a machine-learning risk and fraud detection system supporting large-scale mobile transaction volumes. ### [This Rocket Ain't Stopping - Achieving Zero Downtime for Rails to Golang API Migration](https://yomu.fyi/post/this-rocket-ain-t-stopping-achieving-zero-downtime-for-rails-to-golang.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Lian Yuanlin - Published: Oct 18, 2016 Grab transitioned its public passenger app APIs from a legacy Rails application to a Golang service-oriented architecture to consolidate its codebase and engineering teams. Initial attempts to proxy traffic through a cloned Rails server via gRPC were abandoned after encountering TCP load imbalances during autoscaling events and memory leaks in the gRPC Ruby gem. The team pivoted to direct logic migration, porting Ruby logic directly into Go while decomposing modules into standalone services. Verification relied on log-based load testing and live shadow testing, where write operations were safely validated using mock data access layers that evaluated expected database outcomes. Production rollout progressed endpoint-by-endpoint using requests-per-second traffic throttling and prewarmed AWS Elastic Load Balancers before executing the final DNS switch. ### [Grab Vietnam Careers Week](https://yomu.fyi/post/grab-vietnam-careers-week.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Grab Engineering - Published: Oct 14, 2016 Grab announced its first Grab Vietnam Careers Week, held in Ho Chi Minh City from 22 to 26 October 2016, aimed at hiring engineers to improve regional transportation and reduce congestion. At the time, Grab operated on 23 million mobile devices supported by 460,000 drivers across Southeast Asia. The announcement features an interview with Singapore-based iOS engineer Hai Pham and Android engineer Son Nguyen discussing team culture, regular hackathons termed "Grabathons", and relocation to Singapore. Technical candidates undergo a Codility test and are evaluated on clean mobile architecture, testing, and performance maintenance. The engineers also offer advice on apartment hunting through online community forums and adapting to life in Singapore. [Newer posts](https://yomu.fyi/page/74.md) ยท [Older posts](https://yomu.fyi/page/76.md)