Sebastian Sastre
Systems architect and infrastructure engineer with 23 years of total production experience and over a decade of high-velocity remote delivery for premium US, Canadian, and European tech platforms. Specializes in production-grade Rust, petabyte-scale data pipelines, and low-level Linux/Debian systems optimization.
A pioneer in agentic engineering, operating with an architecture-over-syntax mindset since mid-2025. Utilizes a custom-built, spec-oriented AI orchestration harness with institutionalized review gates (rather than "vibe-coding") to drive multiple complex, parallel infrastructure workstreams simultaneously. Proven capability to manage raw physical constraints, high-throughput distributed state, and resilient event-driven data planes at scale.
CORE CAPABILITIES & AGENTIC STACK
- Agentic Orchestration: Spec-First Prompt Decomposition, Multi-Workstream Management, Railed Planning Structures, Cursor (Daily), Custom Spec-Driven AI Harnesses.
- Systems Programming & Languages: Production Rust (Tokio, Async, Caching, Systems Testing), Go (Multithreaded tooling), Python, Advanced Bash, Pharo Smalltalk.
- Infrastructure & Operating Systems: 23-Year Linux Bedrock (Debian, Ubuntu, CentOS), Bare-Metal Hardware Configuration, Process-Level Debugging, Kernel Log Diagnostics, Docker Infra, Multi-Cloud (AWS, GCloud).
- Data Architecture & Streaming: Petabyte-scale Data Storage, High-Availability PostgreSQL (OLTP Architecture, Complex Replication), Vectorized/OLAP Core Tradeoffs, Kafka-Backed Idempotent Stream Pipelines.
REVIEWS FROM CLIENTS
Championed an AI-first development methodology, integrating Cursor and custom spec-first review frameworks to orchestrate multiple inf...
Championed an AI-first development methodology, integrating Cursor and custom spec-first review frameworks to orchestrate multiple infrastructure workstreams (source parsing, codegen targets, and benchmark harnesses) concurrently.
- Owned, architected, and continuously refactored several high-load, business-critical Rust microservices under strict cryptocurrency exchange engineering standards, focusing deeply on memory efficiency and high concurrency.
- Designed and actively maintain Shakedown, an open-source Rust system-testing crate engineered around real-world infrastructure (Kafka, Postgres, testcontainers) and custom fault injection (Toxiproxy).
Designed, tested, and shipped a high-performance Rust caching system to extend main backend capability beyond 25K operations per secon...
Designed, tested, and shipped a high-performance Rust caching system to extend main backend capability beyond 25K operations per second (ops), directly facilitating the seamless expansion of core production roaming infrastructure to over 1 PiB of data.
- Led a cross-functional team of 4 engineers through a massive 6-month legacy code refactoring initiative to resolve deep technical debt, leveraging advanced Bash, Python, and Docker Swarm to achieve full containerization readiness.
- Engineered a custom, multithreaded stress-testing framework in Go to inject high-volume synthetic traffic into the production pipeline, guaranteeing strict enterprise SLA preservation.
- Supervised large-scale persistence migrations (Voyage to Mapless) and maintained high-availability data infrastructure with a meticulous focus on complex PostgreSQL replication structures.
Led a team of 6 engineers to architect and ship a next-generation, high-volume ad server layer capable of routing massive globally dis...
Led a team of 6 engineers to architect and ship a next-generation, high-volume ad server layer capable of routing massive globally distributed traffic.
- Designed and deployed automated, backward-compatible infrastructure pipelines using GCloud, enabling real-time, zero-downtime global multi-region application deployment.