# Grab > Southeast Asia's leading everyday "super-app" that provides ride-hailing, food delivery, grocery shopping, and digital financial services. ## Articles ### [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. ### [GrabPay Wins Best Fraud Prevention Innovation at the Florin Awards](https://yomu.fyi/post/grabpay-wins-best-fraud-prevention-innovation-at-the-florin-awards.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Foo Wui Ngiap - Published: Oct 12, 2016 Grab won the Best Fraud Prevention Innovation (Community Votes) Award at the 2016 Florin Awards for its GrabPay platform. To support secure cashless transactions across Southeast Asia, Grab deployed a dedicated risk and fraud detection engine when launching GrabPay earlier in the year. The system utilizes machine learning algorithms that continually evolve by analyzing driver, passenger, and travel pattern data across massive transaction volumes. Furthermore, Grab provides full financial protection by covering any unauthorized fraudulent transactions for both passengers and drivers. At the time of the announcement, the platform supported up to 1.5 million daily bookings and exceeded 23 million app downloads. ### [Round-robin in Distributed Systems](https://yomu.fyi/post/round-robin-in-distributed-systems.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Gao Chao - Published: Sep 27, 2016 Building client-side load balancing for Grab's Common Data Service prompted a move from AWS Elastic Load Balancers to DNS discovery due to persistent connection issues and unpredictable scaling events. After patching an open-source library that failed to rotate IP sequences properly, the author evaluated different Go patterns for round-robin routing. A mutex-protected array counter provides the simplest model for basic retrieval, though adding mutations requires careful lock coordination. Alternatively, a dedicated balancer goroutine receiving requests over nested channels enables explicit operation timeouts and centralized event handling at the cost of higher code complexity and channel creation overhead. The author recommends the mutex approach for resource fetching and the goroutine-based design for workload balancing. ### [Why Test the Design with Only 5 Users](https://yomu.fyi/post/why-test-the-design-with-only-5-users.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Avinash Papatla - Published: Aug 26, 2016 Stakeholders often question whether qualitative testing with only five participants yields reliable design findings. The chosen research problem dictates the methodology, with qualitative usability evaluations requiring smaller cohorts than broad quantitative surveys. Jakob Nielsen's 1993 analysis demonstrated that testing with five participants uncovers 75 to 80 percent of usability issues, after which additional users yield diminishing returns. In agile environments, teams maximize efficiency by iterating designs across successive rounds of five participants rather than testing large cohorts simultaneously. This five-user threshold applies strictly to qualitative usability testing for specific feature flows rather than opinion gathering, A/B testing, or multi-segment user analysis. ### [Programmers Beware - UX is Not Just for Designers](https://yomu.fyi/post/programmers-beware-ux-is-not-just-for-designers.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Corey Scott - Published: Jul 5, 2016 Software engineers frequently overlook user experience when designing APIs, SDKs, and code-level functions. Usability issues arise across various technical interfaces, from mobile apps forced to coordinate multiple round-trip network calls to ambiguous function signatures that obscure boolean arguments. To counter this, engineers can apply a five-question discovery framework to identify user identity, core objectives, user capabilities, ways to reduce user burden, and familiar paradigms. Practical remedies include sacrificing strict RESTful separation to merge mobile endpoints, placing validation logic inside internal RPC servers, and replacing boolean arguments with explicitly named helper functions. Ultimately, treating calling systems, end users, and fellow programmers as users shifts implementation complexity from consumers to servers. ### [Grab You Some Post-Mortem Reports](https://yomu.fyi/post/grab-you-some-post-mortem-reports.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Lian Yuanlin - Published: Feb 4, 2016 Grab uses a Service-Oriented Architecture to deploy features quickly, but unfamiliarity across teams makes cross-service production debugging difficult. Historical incident reports lacked context, diagnostic details, impact data, and timelines, leaving outside engineers unable to learn from past outages. To address this, Grab established a four-pillar framework for post-mortem reports covering chronology, context, empowerment, and solutions. The approach mandates blameless, educational write-ups that categorize post-incident improvements across people, product, and process dimensions. Final reports undergo peer reviews by engineers from external teams to ensure clarity and remove bias. ### [The Curious Case of the Phantom Instance](https://yomu.fyi/post/the-curious-case-of-the-phantom-instance.md) - Company: [Grab](https://yomu.fyi/company/grab.md) - Author: Lian Yuanlin - Published: Dec 28, 2015 Datadog dashboards for the grab\_attention cluster displayed periodic 1.5X step increases in Elastic Load Balancer (ELB) health check requests and ElastiCache Redis connections, creating the illusion of an untracked instance running outside Auto Scaling Group records. Inspecting instance hostname tags revealed that the existing two instances were simply receiving elevated ping counts from the load balancers. AWS Support clarified that ELB scaling events provision new nodes while keeping old nodes running for roughly 90 minutes to handle cached DNS clients. Investigation also revealed that two separate ELBs were attached to the cluster, altering expected request baselines. Furthermore, the application's health check endpoint initiated a non-pooled Redis connection on every request, directly translating load balancer pings into database connection spikes. [Newer posts](https://yomu.fyi/company/grab/page/11.md)