crisfon6
I build AI systems that run in production.
I build agentic systems, MCP workflows, and LLM pipelines that run against real data at scale.
I start with who it hurts and what it costs. The code comes last.
Cristhian Fonseca · Open to remote Technical Lead roles with US teams (CT/ET overlap) · full-time or contract
Full work history →
I'm Cristhian Fonseca — a Technical Lead with 5+ years building cloud-native FinTech and banking platforms.
Technology serves the business, not the other way around. I build what moves the metric, not what looks good in the codebase.
- NOW
- Technical Lead · Prosperas · May 2025 – PresentCredit marketplace inside a major telecom's Super App
- BASED
- Colombia · Remote (CT/ET overlap)
- CREDENTIALS
- B.Eng. Systems Engineering · Universidad Autónoma de Bucaramanga (UNAB)Technical Degree in Computer Systems · SENAClaude Code in Action · Anthropic
- STACK
- AI & agents — Claude API · Claude Code (skills, headless, sub-agents, hooks) · MCP servers
- Cloud & infra — AWS CDK · ECS Fargate · Lambda
- Backend — Python · FastAPI · SQLAlchemy
- Frontend — Angular · ECharts · SvelteKit
5+
Years shipping to production (since 2021)
~100K
Monthly active users on my current platform
−43%
AWS bill after the cost audit I led
30×
Faster bulk data export (638K rows in 21 s)
Systems I've shipped.
- AI · MCP · AGENTS
An MCP server that lets the business query production data — and get the right number
Executives, managers and analysts wanted answers from production data without waiting on engineering. The first version of the natural-language-to-SQL assistant returned plausible but wrong numbers.
Reconciled exactly against independent countsRead the case - AI · ORCHESTRATION
A multi-agent engineering org that ships — and reviews its own work
Agents can write code. The hard part is who reviews it. I built the harness around that question: agents plan, build and review each other's work under explicit gates.
Two blind judges review every branch independently; a separate fixer applies only confirmed defects.
2 blind judges + synthesizer + fixerRead the case - FINTECH
Digital credit marketplace inside a telecom Super App
A major telecom operator wanted to offer credit to the users of its Super App — fully digital, with no paperwork and no branch visits.
45M-user ecosystemRead the case - CLOUD · FINOPS
Cutting the AWS bill by 43% without touching production performance
The AWS bill had grown for years across 17 enabled regions, with no budget, no anomaly alerts and no one who could say what each resource was for.
Refused a tempting downsize: the production cluster averaged 12.7% CPU, but its p99 was 97.5%.
ECR 229 GB → 21 GBRead the case
Measure before you execute.
Before a destructive data operation I write down the expected numbers and rehearse on a copy of production; that rehearsal once caught 6 errors before they reached users.
Hiring a senior engineer for a US team? Email me.
I connect with founders, CTOs, and senior engineers shipping products at scale.
- Remote · US teams (CT/ET overlap)
- Full-time or contract
- References on request
Production blueprints from systems that actually run
Architecture diagrams, deployment guides, cost breakdowns, and working code. Shipped from production, not tutorials.