Nice to Meet You, I’m Darong Mean.
I work at Zimpler , a fintech company in Gothenburg that specializes in account-to-account payment solutions. My primary role involves developing and maintaining bank integrations across Brazil, Finland, and Sweden. This includes working with various payment standards such as PIX , SEPA , PSD2 , and Swish .
I’m particularly passionate about working with Clojure , Go , continuous delivery practices, and extreme programming methodologies.
Beyond my day-to-day work, I enjoy exploring a wide range of technical interests – from property-based testing and DevOps to web development and information architecture. I also have a keen interest in startup culture.
My CV is available at https://darongmean.com/resume.pdf .
Experience
2023 - Now: Software Developer at Zimpler
- Enhanced robustness of integrations with unreliable banks, increasing acceptance rates by up to 30%.
- Optimized deposit flow, improving acceptance rates by up to 30% and reducing session time by 20%.
- Implemented an integration feature, reducing a significant amount of operation costs.
- Implemented instant refund integrations with Brazilian banks, enhancing the user experience.
- Created deposit, payout, and reconciliation integrations with Brazilian banks.
- Created deposit, payout, and reconciliation integrations with Finnish banks using SEPA transfer.
- Developed deposit, payout, and reconciliation integrations with Swedish banks, supporting PSD2 APIs and fallback solutions.
- Implemented B2B payments supporting Bankgiro, Plusgiro, and co-signing.
- Resolved issues with bank integrations, ensuring systems processed millions of transactions monthly.
2022 - 2023: Spring Java Backend Developer at GameGrid
- Enabled the business to accept Bitcoin and other cryptocurrencies by integrating with Fireblocks.com.
- Implemented Stripe.com integration and addressed support queries about payment failures and card declines.
- Improved application logs with Opentelemetry.io, boosting monitoring and troubleshooting.
- Enhanced alert system with OpenSearch.org for better incident response.
- Fixed race condition issues with Paygarden.com gift cards, streamlining processing and preventing financial losses.
- Improved Robux withdrawal process for a more efficient customer experience.
- Developed a holiday raffle game, adding an engaging feature and retaining customers.
- Implemented SMS rate limits via Telnyx.com, ensuring reliable communication.
- Enhanced customer communication with Onesignal.com for email, SMS, and push notifications.
- Integrated Adurite.com and Iterable.com, enhancing platform capabilities and user experience.
2021 - 2022: Software Developer at Paymentology
- Resolved support tickets for failed payments, chargebacks, and MTI timeouts.
- Resolved production issues alerted by PagerDuty and Standby channels.
- Developed and implemented credit card management APIs using Spring Boot.
- Maintained MasterCard and Visa processing systems, handling millions of transactions daily.
2021 - 2021: Data Platform Engineer at Digital Commerce Intelligence
- Migrated applications from Azure to AWS, reducing operational costs.
- Maintained a data pipeline engine, ingesting data from popular Southeast Asian e-commerce platforms like Shopee.com and Lazada.com.
- Pre-processed pipeline data for analytics, enabling merchants to track product performance more effectively.
2019 - 2021: Clojure Developer at Rakuten Ready
- Maintained APIs for the merchant live dashboard, used by 2500+ stores in the United States, processing 34 million store visits per month, tracking pickup orders, and providing real-time statistics for orders.
- Optimized PostgreSQL query performance, reducing response time from 50s to 30s.
- Converted SQL queries to Apache Beam streaming jobs, reducing stats endpoint response time from 30s to 1s.
- Created a Clojure wrapper for Apache Beam.
- Improved test robustness with generative end-to-end tests and migrated Postman tests to Clojure tests.
- Enhanced test coverage for AWS SNS and Twilio integrations.
- Migrated a simulator tool from TypeScript to Clojure, reducing tool fragmentation.
2012 - 2018: Various positions at Khalibre
- Liferay Team Lead/Technical Line Manager
- Expanded the development team from 2 to 7 developers.
- Enhanced team knowledge in continuous integration, pair programming, and the Mikado method, fostering a culture of high-quality code and system improvements.
- Designed technical solutions for Crosswired.com and related projects.
- Upgraded Liferay from 6.2 to 7.0, enabling the business to leverage the latest technology for future projects.
- Integrated Single Sign-On (SSO) between Liferay, SAP Netweaver, SAP R3, and Keycloak, facilitating customer onboarding.
- Integrated SSO between SAP Portal and MS Reporting Service 2012 for a client’s finance team.
- Workstream Leader
- Established development and quality assurance processes, including version control, build, and release management.
- Created comprehensive learning materials for new team members to facilitate rapid onboarding.
- Implemented Liferay with social collaboration features and integrated it with SAP XLSO, ensuring compatibility across organizations and confidence in the security model.
- System Developer
- Delivered EHP 6 Upgrade + HCM Renewal Pack 1, including implementing the HCM Admin Landing Page and cleanup of standard modifications and enhancements.
- Completed a performance management project, implementing a program to check appraiser consistency and enhancing appraisal document search criteria.
- Developed a C# tool using Visual Studio 2010 to migrate QuickR content to SAP Portal KM, significantly speeding up the process and reducing manual work. The tool can also be sold as a standalone product.
- Implemented a CAPTCHA tool with image processing functionality and conducted extensive performance tuning.
- Revived and significantly reworked an abandoned project after the original author left the company.
Personal Projects
- Failed Payments Notify - For Shopify merchants to keep track of their payment solutions.
- Internal URL - For developers to quickly open a URL on mobile devices while working on a desktop.
Expertise
- APIs, REST, SOAP, XMLRPC
- Backend: Clojure, Go, Java (J2EE, Liferay, Spring, Spring Boot), ColdFusion…
- Frontend and single page application: Clojurescript, React JS, Tailwind CSS, CUBE CSS…
- Database: PostgreSQL, MongoDB…
- Cloud: AWS, GCP, Ansible, Docker, Terraform…
Practices
- Extreme Programming, lightweight lean methodology
- Devops, continuous integration, continuous delivery
- Pragmatic craftsmanship
- Testing and automation
Contact
Not finding what you’re looking for? You are welcome to contact me for any kind of questions.