Sebastián Orrego @saitama
Platform & AI infrastructure engineer
I build the layer underneath other people's work: the platform that lets engineers ship without touching cluster state, and the retrieval systems that give AI agents real context instead of plausible guesses. Most of what I do is turning something that only I know how to run into something a team — or an agent — can run without me.
Skills
| Platform engineering | Kubernetes · GitOps / ArgoCD · AWS · Terraform · CI/CD · Observability |
|---|---|
| AI infrastructure | MCP servers · Retrieval (passage indexing, RRF, cross-encoder rerank) · Evaluation harnesses & LLM-as-judge · Agent tooling and orchestration |
| Data & storage | PostgreSQL · Multi-tenant isolation · Vector search · Schema design |
| Languages | Go · Python · TypeScript · Bash · SQL |
Work
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Rebuilt a corporate retrieval system that was returning noise
A search layer over ~1,100 internal documents was tuned with four hand-picked similarity thresholds. Whole classes of query scored so low that correct and incorrect answers were indistinguishable.
Replaced whole-document embedding with passage-level indexing, fused lexical and semantic ranking with reciprocal rank fusion, and added a cross-encoder rerank on the top candidates. Deleted every hand-tuned threshold.
On the queries that previously collapsed to near-zero relevance, scores went from ~0.02 to ~0.84. The system stopped needing a human to retune it.
Python · PostgreSQL · vector search · cross-encoders
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Built an internal developer platform
Shipping an application meant hand-editing GitOps manifests, clicking through ArgoCD, and knowing which of several clusters was the right one. Every deploy was a small act of tribal knowledge.
Designed a CLI and API where the application declares its intent and the platform owns every side effect — GitOps commits, image promotion, rollout, rollback. Application teams never touch cluster state directly. JSON-first output so both humans and agents can drive it.
Deploys became self-service. The platform, not a person, became the thing you ask when a rollout is stuck.
Go · Kubernetes · ArgoCD · AWS · GitOps
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Multi-tenant isolation for a data product
A single-tenant system had to serve multiple customers whose data could not be allowed to mix, without a rewrite.
Isolated tenants at the PostgreSQL schema and role level rather than with row-level security — a coarser boundary the database enforces itself, instead of one that depends on every query being written correctly forever.
Cross-tenant reads became impossible at the engine level rather than unlikely at the application level.
PostgreSQL · Go · AWS
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Debugged an evaluation pipeline everyone blamed on the model
A nightly batch inference pipeline scored far below expectations. The consensus was that the judge model was simply not good enough.
Instrumented the path between the pipeline and the model instead of tuning prompts. Found five separate defects in that path, each of which degraded output in a way that looked exactly like poor model judgement.
Scores recovered without changing the model or the prompts. See `saitama_challenge` — this one is the puzzle.
Python · LLM APIs · batch inference
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Private cross-environment networking
Services in separate AWS environments needed to reach each other without traversing the public internet, and without a flat network that would undo the reason they were separate.
Designed a PrivateLink-based topology: explicit, one-directional, per-service endpoints rather than VPC peering.
Each connection is something someone deliberately granted, and is visible as its own resource.
AWS PrivateLink · Terraform · Kubernetes
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This site
A CV is a document you read. An agent asked about me has to scrape it, guess, and often invent.
Made one origin serve four representations of the same corpus: an ASCII CV for terminals, a page for browsers, a stateless MCP server for agents, and llms.txt for crawlers.
You are reading one of them right now.
Node.js · MCP · nginx · AWS · Cloudflare
How I work
- Make the boundary something the system enforces, not something a reviewer remembers to check.
- If a threshold has to be hand-tuned, it is a bug that hasn't been diagnosed yet.
- When the model looks stupid, instrument the transport first.
- The goal of a platform is to stop being the person who knows how to run it.
Availability
ask
curl saitama.shhttps://saitama.sh/mcp