Resume · Updated
Juan Diego Sierra Fernández
Platform Engineer | Site Reliability Engineer | DevOps | AI Harness Engineer | Blockchain Engineer
Summary
Infrastructure, platform, and site reliability engineer with 10+ years of experience building and operating scalable systems, and a track record of leading engineering teams.
I have put AI tooling into production to improve how teams build and ship software, worked at early-stage startups where I standardized processes from scratch, and at large corporate environments with strict procedures and compliance requirements.
Having worked as both a software developer and an infrastructure engineer, I have a thorough understanding of the entire software delivery lifecycle.
Interested in leadership positions such as Team Lead, Staff Engineer, Principal Engineer, or Head of Platform.
I encourage you to read my manifesto to see if my engineering mindset aligns with your company's values.
Open Source
Contributions
claude-code-templates +31K ★
Claude Code community templates and reference configurations.
helm-unittest +1.3K ★
BDD-style unit test framework for Kubernetes Helm charts.
opentelemetry-helm-charts +500 ★
Official OpenTelemetry Helm charts for Kubernetes.
openfga/helm-charts +40 ★
Official Helm charts for OpenFGA authorization service.
My Projects
contributor-report +60 ★
GitHub Action that evaluates contributor quality and helps teams catch spammy AI-generated PRs with objective signals.
enterprise-agent-plugins
Extensible plugin system for enterprise AI agent pipelines and workflows.
enterprise-agent-operator
Kubernetes operator for deploying and managing enterprise AI agents at scale.
observability-cli
CLI tool for querying and analyzing observability data across Grafana, Loki, and Mimir.
Experience
Site Reliability Engineer
Ionik Tech
- Founding member of a newly created SRE team, built to standardize, deploy, and maintain customer-facing applications in production in a high-traffic, on-premise environment.
- Design and evolve a scalable, standardized deployment system for multiple production customers.
- Manage the full application lifecycle through GitOps with GitLab and ArgoCD.
- Package and version applications with Helm on on-premise Kubernetes clusters.
- Run proactive observability and monitoring with Prometheus and Grafana.
- Manage artifacts and dependencies with Nexus.
- Implement AI-driven solutions to automate deployment pipeline tasks, reducing manual intervention and delivery times.
- Ensure the reliability, performance, and stability of critical platforms under demanding traffic conditions.
Platform Engineer Team Lead (AI Platform)
Maisa
- Led a team of 6 engineers and reported directly to the CTO. Owned team organization, priorities, and engineering practices.
- Owned architecture decisions and led the creation and review of RFCs.
- Acted as an enabler for other engineering teams — reducing friction and providing the platform, tooling, and processes they needed to ship faster.
- Drove AI adoption across the SDLC, improving engineering speed, developer productivity, and delivery quality.
- Built production-grade AI workflows with LiteLLM, Claude Code, OpenCode, and OpenClaw: agents, plugins, skills, and commands for internal engineering use cases.
- Operated the platform on AWS, supporting both Maisa's own SaaS product and customer-deployed Helm chart installations.
- Drove FinOps and cloud cost optimization: keeping spend visible, cutting waste, and making sure infrastructure costs actually made sense.
- Administered Jira across the organization, including project configuration, workflows, automations, and board management.
- Implemented security and compliance standards including SOC 2 and ISO 27001.
- Collaborated with developers to design and operate the full CI/CD lifecycle with GitHub Actions.
- Released and maintained a public Helm chart, and managed Kubernetes, OpenShift, Karpenter, and ArgoCD for continuous delivery.
- Provisioned infrastructure with Terraform, Terragrunt, Pulumi, and Crossplane using a GitOps approach.
- Built and operated monitoring and observability with Grafana, Mimir, Loki, Tempo, and OpenTelemetry.
- Worked primarily with Go, Python, and TypeScript.
Site Reliability Engineer
The Workshop
- Standardized CI/CD processes across seven product verticals, improving consistency and deployment quality.
- Managed and maintained more than 50 Kubernetes clusters supporting large-scale production workloads.
- Created and maintained Docker images, Helm charts, GitLab pipelines, and Ansible playbooks to support scalable and automated platform operations.
- Contributed to open-source initiatives, focusing on cloud-native and observability tooling.
- Mentored junior SREs, providing technical guidance and fostering skill development.
Platform Engineer
Bdeo
- Designed and maintained cloud-native and serverless architectures on AWS.
- Managed the company's entire AWS infrastructure, including CloudFormation, API Gateway, Lambda, CloudFront, Route 53, EC2, DynamoDB, RDS, and Fargate.
- Drove DevOps culture adoption across teams, improving CI/CD workflows with GitLab pipelines and developing internal tooling.
- Designed and developed horizontal platform services (blockchain, notifications, language, and auth services) to accelerate product development.
- Collaborated with the support team to diagnose and resolve complex production issues.
- Assisted developers by providing technical guidance and helping unblock challenges.
Senior Software Developer
Bdeo
- Worked as a senior developer within the product team, performing code reviews, designing new services, refactoring legacy code, and promoting programming best practices.
- Designed, deployed, and maintained AWS infrastructure supporting core product services.
Senior Blockchain Developer
Airbus Defence and Space
- Led and developed international blockchain projects with teams across Germany, Italy, Spain, and France.
- Designed and implemented a custom blockchain from scratch using Python and LevelDB.
- Served as team lead on a project for the Port of Cartagena using Hyperledger Fabric within the Alastria Network.
Embedded Software Developer (Internet of Things)
Altair
- Developed a customized fork of Node-RED using Node.js.
- Built software for IoT devices in C/C++.
- Gained hands-on experience with protocols and technologies including Bluetooth, RabbitMQ, ThingWorx, Sigfox, LoRa, RFID, and WiFi.