Marius Nicola Selective availability

If it can't be measured, it's not real. If it can't be reproduced, it's broken. I build systems that stay correct when the traffic triples.

2002→2026
18+ yrs C# & production engineering

MariusNicola

Senior Software Engineer & Systems Architect, based in Bucharest Scroll

01. About

I design boring, composable primitives that survive production.

15+ years in production engineering. I don't chase hype cycles — I build systems that stay correct when the traffic triples, the regime shifts, or the intern pushes to main. Engagements concentrate around systems that have outgrown their architecture, optimization layers rebuilt natively in .NET, and quant infrastructure that has to match live reality — to the tick.

Toptal · Verified Expert in Engineering · Top 3%

02. Experience

Toptal clients — US & EU2021–Present

Shopify Architect

Nine brands across fragrance, fashion, jewelry, apparel, and B2B — including Pernod Ricard. Event-driven storefronts, state-machine carts, multi-market inventory automation, A/B tests that doubled conversion rates, and an ML-based sizing engine that cut returns.

Uniper — Energy2020–2023

Senior Software Developer → Technical Lead

Industrial data engineering over 200M+ rows and 6 power-plant types on Snowflake. Cursor-based procedures that timed out rebuilt as deterministic pipelines that finish in hours; grid bids became plannable 1–2 years out.

Enterprise fleet-management SaaS2017–2020

Senior Fullstack Developer

Platform tracking 5M+ trucks: visual workflow builder, geofencing, one database per tenant, and query paths taken from seconds to 30ms. GPS route replay with physics-based outlier correction.

Ad-tech startup2015–2016

Platform Developer

Real-time bidding aggregation over billions of RTB records — a queue and worker-pool architecture with throughput faster than the ingest rate.

Romanian platform company2009–2015

Software Developer — two internal platforms

Seven years building a managed-print-services platform and a shop-management platform end to end. C# / .NET and SQL Server.

German ERP agencyEarly 2000s

First developer role — automotive ERP

Hired on scholarship. ERP for major European automotive brands; queue architecture importing millions of parts. VB6 and SQL Server, where the discipline started.

03. Skills

C# 18 yrs .NET Core JavaScript 15 yrs TypeScript React Node.js SQL 11 yrs PostgreSQL Snowflake Shopify / Liquid 7 yrs GraphQL Azure & AWS TDD 6 yrs CI/CD System Design HPO — TPE, CMA-ES Quant Systems AI Agents

04. How I Think

01

If it can't be measured, it's not real.

Every claim — speed, correctness, reliability — needs a number, a baseline, and a method. "Feels fast" doesn't clear the bar.

02

If it can't be audited, it's not trusted.

No black boxes, no magic pipelines, no AI output without gates and traceability. Git-backed audit trails over opaque orchestration.

03

If it can't be reproduced, it's broken.

Same seed, same result — on your machine, in CI, in production. "Works on my machine" is a design failure, not a quirk.

04

If optimization hits discontinuities, the design is wrong.

Hard if/else in an optimization problem is a gradient killer. If the optimizer can't see the slope, you'll never find the minimum.

05. Education

M.Sc. Computer Engineering

Polytechnic University of Craiova — five-year degree

1997–2002

Informatics

National College Carol I, Craiova

1993–1997

06. Current Focus

OptiSharp

Native C# hyperparameter optimization — open source, MIT

Open Source

Quantitative trading systems

Deterministic fills, crash-aware regimes — paper = live, to the tick

Ongoing

AI automation & agents

Gated, auditable pipelines — no output without traceability

Ongoing

07. Contact