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Hi there 👋

I am currently a Cloud Technical Specialist at Enfinity Solutions Limited, with my current role focused on:

  • Architecting and delivering cloud-native solutions to our customers on AWS and Alibaba Cloud, and
  • Daily operations and maintenance of our on-premises GitLab and Kubernetes infrastructure

In my spare time, I write blog posts on DevOps practices and tools on my personal website: donaldsebleung.com

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Work Experience

Cloud Technical Specialist at Enfinity Solutions Limited (2023/07-present)

Terraform migration to OpenTofu (2024/05; 1 month)

Performed a successful migration of all existing internal and customer-owned Terraform IaC projects to OpenTofu following the officially supported procedure outlined in the OpenTofu documentation, for a total of 8 projects

Business impact

Eliminated the potential legal risks of managing internal and customer-owned infrastructure with proprietary tooling, ensuring the sustainability of affected IaC projects in the long run

Rancher RKE2 OIDC integration with Dex (2024/02; 1 month)

Implemented a centralized identity management solution backed by Active Directory for on-premises Rancher RKE2 cluster, leveraging Dex as the OIDC connector

Business impact

Consolidated authN + authZ under a single umbrella across on-premises IT infrastructure with Active Directory as the sole IdP and single source of truth, ensuring the scalability of access management for on-premises resources in the long term

Kasten K10 DR drill (2024/01; 1 month)

Performed a successful on-premises DR drill for GitLab EE 16.x and supporting Rancher RKE2 infrastructure with Kasten K10 for cross-cluster application level backup and disaster recovery, with:

  • Ansible for automated provisioning of new Rancher RKE2 cluster in a 3-server HA control plane setup with CIS-1.23 hardening
  • A confirmed RPO of 48 hours based on daily Kasten K10 backup
  • A confirmed RTO of 24 hours based on the actual DR drill duration for complete service resumption of GitLab EE 16.x (and other supporting services)
Business impact

Confirmed that the DR handbook procedure is fully functional and actionable, ensuring business continuity in the event of a complete infrastructure failure

Kasten K10 DR planning and evaluation (2023/12; 1 month)

Drafted a comprehensive DR handbook for on-premises GitLab EE 16.x installation and supporting Rancher RKE2 infrastructure leveraging Kasten K10 for cross-cluster application-level backup and recovery, followed up by an initial DR test drill on AWS leveraging an automation stack for efficiency, reproducibility and standardization, developed in-house with:

  • OpenTofu for provisioning AWS resources mirroring the on-premises infrastructure
  • Ansible for provisioning a fresh Rancher RKE2 cluster in a 3-server HA control plane setup with CIS-1.23 hardening on provisioned infrastructure
  • GitLab CI with manual approval step for E2E validation of the complete OpenTofu + Ansible automation stack
Business impact

Confirmed the feasibility of performing the procedures outlined in the DR handbook and uncovered fundamental limitations of a lift-and-shift recovery of on-premises Rancher RKE2 infrastructure to AWS, laying the groundwork for performing a complete DR drill going forward and ensuring business continuity in the event of a complete infrastructure failure

GitLab EE 16.x installation and tuning (2023/07-2023/09; 3 months)

Deployed GitLab EE 16.x to on-premises Rancher RKE2 cluster to accelerate software delivery and enable DevOps, DevSecOps and GitOps workflows, with:

  • Rancher RKE2 deployed in HA mode (3 server nodes) for fault tolerance
  • Rancher RKE2 deployed with CIS-1.23 profile enabled for security hardening
  • Prometheus and Grafana for monitoring, observability and email alerting
  • Flux v2 for cluster-wide GitOps management with Microsoft Teams notifications and alerting
Business impact

Enabled rapid prototyping, drastically reduced time to production and standardized software delivery processes with a security-first approach

Multi-cloud monitoring, observability and alerting (2023/08; 1 month)

Implemented dashboards exporting instance and host-level metrics from 30+ cloud VMs across AWS and Azure for a major airline company, with:

  • Amazon CloudWatch for monitoring and observability
  • Amazon SNS for email alerting on storage-related events
  • AWS Lambda with a container-based deployment model for recurring critical alarms
  • GitLab CI for an automated DevSecOps workflow involving multiple pipelines:
    • Terraform pipeline with GitLab-managed remote backend and manual apply step for semi-automated provisioning and management of AWS infrastructure (CloudWatch, SNS)
    • Container-oriented pipeline with unit tests, SAST, image build, Trivy scan and push to Amazon ECR for automated deployment and quality assurance of Lambda-based microservices
Business impact

Real-time visibility into AWS and Azure infrastructure, improving SLA and reducing incident response times

Specialist in IT consulting at China Resources Enterprise Limited (2021/07-2023/05; 1 year 10 months)

Assisted in meeting room setup for videoconferencing, Windows desktop and laptop software installation, Windows and Outlook troubleshooting, printer troubleshooting at Wan Chai HQ office

FortiGate to H3C HQ firewall replacement (2023/01-2023/03; 3 months)

Oversaw the technical execution of the HQ firewall replacement from FortiGate to H3C for a BU in the catering industry, jointly devised and executed an appropriate action plan with a Chinese network service provider during off-hours to minimize business disruption and ensure business continuity

Business impact

Improved the network security of the affected BU by retiring an EOL firewall product and contributed to the enforcement of Chinese SOE compliance requirements

Leased line replacement (2022/10; 1 month)

Oversaw the replacement of a leased line affecting the HQ network topology for a BU in the catering industry, devised and executed an appropriate action plan modifying the HQ FortiGate firewall configuration during off-hours to minimize business disruption and ensure business continuity

Business impact

Optimized the network topology for the affected BU, reducing network latency and error rates

Software Developer (Intern) at M-Labs Limited (2020/06-2020/11; 6 months)

Implementing sorting network for ARTIQ control system (2020/09-2020/11; 3 months)

Implemented the sorting network for the ARTIQ control system used in physics experiments, leveraging:

  • nMigen for its Python DSL
  • Yosys / SymbiYosys for formal verification

Porting Minerva RISC-V soft core from Verilog to nMigen (2020/06-2020/08; 3 months)

Ported the Minerva RISC-V (RV32M) soft core from Verilog to nMigen, leveraging:

  • Python for its powerful abstractions and language features
  • Automated SMT solvers (Yosys, SymbiYosys) for verifying the functional correctness of the FPGA core

Teaching Assistant (Intern) at BSD Education (formerly BSD Academy) (2016/08; 2 weeks)

Assisted in teaching duties for 2 classes of students aged 8-10 on frontend development with HTML5+CSS3+JS

Education

BEng. Computer Science and Engineering (4Y), The Hong Kong University of Science and Technology, Class of 2021, First Class Honors, GGA: 3.742

Community

Contact

Please kindly refer to my profile and CV for details.

Donald Sebastian Leung's Projects

homebrew-admin icon homebrew-admin

Administration utilities authored and/or packaged for Homebrew by Donald Sebastian Leung.

homebrew-games icon homebrew-games

Games authored and/or packaged for Homebrew by Donald Sebastian Leung.

homebrew-misc icon homebrew-misc

Miscellaneous utilities authored and/or packaged for Homebrew by Donald Sebastian Leung.

html5up-anything-templates icon html5up-anything-templates

This repo contains all the HTML5UP templates which are classified as "Recommended for: Anything" in Pixelarity.

html5up-exclusive-templates icon html5up-exclusive-templates

This repo contains all the HTML5UP templates that are not provided by Pixelarity. Please note that these templates are NOT owned by me. I am merely a collector of these templates. Go to http://html5up.net for all of the templates available at HTML5UP.

image-rotator icon image-rotator

An example of a rotating image in a webpage. Credit goes to W3Schools (http://w3schools.com)

image-switcher icon image-switcher

Also called the "Product Switcher". This project makes certain images fade in and out at set time intervals. Now that it is successful, I could use it in next year's JA Company Website if I join it next year and become IT Director.

innovision-website icon innovision-website

All the code for the Innovision Website (Kellett JA Company Programme 2014-2015)

internal-search-engine-prototype icon internal-search-engine-prototype

A prototype of an internal search engine that I could potentially use in a website. However, it is a very simple search engine and has to be updated manually to show new results.

iron-lambda icon iron-lambda

My copy of (possibly modified portions of) Iron Lambda by Ben Lippmeier with the explicit aim of making it easier to step through the proofs interactively using CoqIDE.

javascript-to-brainfuck icon javascript-to-brainfuck

A collection of convoluted Brainfuck programs that translate to very simple JavaScript code. These show that even seemingly trivial tasks in high-level programming languages can be very difficult to program in low-level programming languages. MIT License

js-library-demo icon js-library-demo

A JS Library where all the needed functions are stored as properties of the 'library' object. You can view it as a showcase of what I can now do with Javascript.

jstester icon jstester

A simple custom Javascript TDD Framework that requires minimal setup. Open Source

jw-ih-exercises-checklist icon jw-ih-exercises-checklist

A checklist for tracking my progress through James Wilcox's "Exercises on Generalizing the Induction Hypothesis"

k8s-intro-eks icon k8s-intro-eks

Assets for the "Introduction to Kubernetes with Amazon EKS" article on Dev.to

kellett-sixth-form-blog icon kellett-sixth-form-blog

This used to be the Kellett Sixth Form (Youde) University Blog. However, as of 07/10/15, it has been officially scrapped.

latex icon latex

All my LaTeX projects will be here! Credits to Overleaf (http://overleaf.com) for the LaTeX tutorials.

latex-examples icon latex-examples

Some LaTeX examples for my own reference (psssst ... I'm learning LaTeX ... ).

linux-intro-mad-libs icon linux-intro-mad-libs

Mad Libs respin of "What is Linux and Why There are 100's of Linux Distributions?" by It's FOSS

linux-rocks icon linux-rocks

Proof of concept voting app. Vote for your favorite Linux distribution!

local-storage-main-experiment icon local-storage-main-experiment

A HUGE experiment on Local Storage. When the experiment is completed, it will be available for download. If the experiment is successful, I may use it in future projects.

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