Independent consultant · part of Bytecode

Rails rescue, product ownership, and practical AI

I help founders and product teams stabilize, modernize, and scale Ruby on Rails applications — then connect them to useful AI workflows.

I am a senior Ruby/Rails developer and technical consultant from Zagreb, Croatia, with 15+ years of experience building production web applications, internal tools, data pipelines, and backend systems.

I have led Rails development teams, and I can also own delivery independently when you need one senior person to take a product, migration, integration, or rescue mission from diagnosis to production.

My best fit is remote contract work where an existing Rails product needs experienced hands: upgrades, refactoring, performance work, production debugging, infrastructure cleanup, payment/CRM integrations, or practical AI/LLM automation.

Available for: remote contract, freelance, part-time consulting, and CTO-for-hire engagements for founder-led SaaS products.

15+

years of backend and Rails consulting

100k+

monthly users served by shipped products

111k

Rails training samples used for public Hugging Face models

250k+

records synchronized through production pipelines

How I Can Help

Senior help for Rails stability, speed, and AI leverage.

  • Ruby on Rails development, maintenance, upgrades, and refactoring
  • Rails rescue work: production debugging, performance fixes, test stabilization, and legacy cleanup
  • Hotwire, Turbo, Stimulus, PostgreSQL, Redis, Elastic, background jobs, and pragmatic full-stack Rails
  • Production ownership: Docker, AWS, DigitalOcean, Heroku, CI/CD, monitoring, and server architecture
  • Stripe/payment integrations, CRM integrations, admin systems, and internal tools
  • AI/LLM integrations: internal copilots, data extraction, workflow automation, RAG-style search, and agent workflows
  • Technical leadership for Rails teams, plus independent end-to-end delivery when needed
  • Technical partner / CTO-for-hire support for non-technical founders and small teams

If you have a Rails product that needs to be stabilized, modernized, scaled, or connected to AI/business automation workflows, email me at vmarcetic@bytecode.hr.

Selected Work

Production systems, rescue work, and practical AI automation.

SayTrue

saytrue.ai

AI customer service platform that answers across chat, voice, and social channels only from approved knowledge, with source citations and human handoff when confidence is low.

Problem: Regulated teams need AI support agents that can explain where answers came from instead of hallucinating or improvising policy-sensitive responses.

What I did:

  • Built a source-grounded AI support platform for web chat, phone calls, Messenger, and Instagram DMs
  • Designed workflows around approved knowledge bases, citations, confidence thresholds, and honest fallback
  • Added voice/transcription flows and supervisor-friendly searchable transcripts
  • Shipped an EU-hosted, GDPR-aware product with an open changelog and demo/contact funnel

Tech: Ruby on Rails, AI/LLM workflows, RAG, voice transcription, omnichannel messaging, GDPR-aware infrastructure

Uskladi.eu

uskladi.eu

Compliance operating system for Croatian and EU organizations managing GDPR, NIS2, DORA, and EU AI Act obligations.

Problem: Compliance work usually lives across spreadsheets, documents, email threads, scans, and disconnected evidence folders, making audits and ongoing readiness painful.

What I did:

  • Built a platform for GAP assessments, readiness scoring, registers, findings, evidence, and audit exports
  • Modeled workflows for GDPR ROPA/DSR/DPIA, NIS2 incident timelines, DORA controls, and EU AI Act inventories
  • Connected technical scanning and compliance findings into one operational workspace
  • Localized the product for Croatian organizations and EU regulatory language

Tech: Ruby on Rails, PostgreSQL, compliance workflows, document exports, security scanning, EU regulatory frameworks

Napster

www.napster.com

Web backend development and R&D support for one of the most recognizable brands in digital music.

Problem: A large, established streaming platform needed reliable backend contributions and fast technical exploration for a new product initiative.

What I did:

  • Contributed to web-facing backend systems inside an established product codebase
  • Supported R&D and prototyping for a new product direction
  • Worked within existing engineering standards and delivery workflows at scale
  • Brought practical subscription/media-product experience from the broader Rhapsody/Napster ecosystem

Tech: Ruby on Rails, PostgreSQL, Redis

Gimme Radio

gimmemetal.com

Music streaming/community product work for Gimme Radio — now Gimme Metal — in the same digital music lineage as Napster and Rhapsody.

Problem: Niche music communities need more than a generic catalog: they need programming, live context, discovery, subscriptions, and reliable fan-facing product flows.

What I did:

  • Worked on production product/backend development for a music streaming and fan community platform
  • Applied experience from subscription-style media products and the Napster/Rhapsody ecosystem
  • Helped support consumer-facing music product workflows where reliability and iteration speed mattered

Tech: Ruby on Rails, music streaming products, subscription-style product workflows, production backend systems

Roomsie

roomsie.com

Medium-term housing marketplace for interns, students, and recent graduates in Washington, D.C.

Problem: After multiple teams failed to deliver, the product needed a focused senior team to stabilize direction, rebuild, and launch.

What I did:

  • Took over an existing troubled build and helped move it toward a working product
  • Implemented payment flows, production features, and core marketplace functionality
  • Fixed and optimized Rails code and RSpec tests while keeping delivery moving

Result: Rebuilt and launched a revenue-generating product in 8 months.

Tech: Ruby on Rails, React, PostgreSQL, Redis, Heroku

RaceChip.hr

racechip.hr

Croatian-market RaceChip webshop built on Spree as a separate ecommerce project from RaceChip.com.

Problem: Vehicle tuning ecommerce needs a clear localized storefront where buyers can find compatible products and complete purchases without confusion.

What I did:

  • Built the RaceChip.hr webshop on Spree
  • Focused on ecommerce storefront flows for the Croatian market
  • Kept this as a separate webshop project from the RaceChip.com application work

Tech: Ruby on Rails, Spree, PostgreSQL, ecommerce

RaceChip.com

www.racechip.com

Java application work for RaceChip, the performance tuning company behind RaceChip.com.

Problem: Established automotive product companies need reliable custom software around their operational and product workflows, separate from regional webshop builds.

What I did:

  • Building a Java application for RaceChip
  • Working in a separate project context from the RaceChip.hr Spree webshop
  • Supporting software delivery for the RaceChip.com company/product ecosystem

Tech: Java, application development, automotive product workflows

Klarx

klarx.de

Work connected to Klarx, a German construction-equipment rental platform for digital machine procurement and rental workflows.

Problem: Construction teams need faster, clearer access to available equipment, rental logistics, and procurement workflows across many machine categories and locations.

What I did:

  • Supported product/platform delivery in a construction-equipment rental context
  • Worked around digital rental and operational workflows for a marketplace-style product
  • Contributed to software used for simplifying equipment procurement and rental operations

Tech: Ruby on Rails, marketplace/product development, operational workflows

Goop

goop.com

Short, focused consulting on ecommerce/product work for Goop, a content-led consumer brand.

Problem: Mature ecommerce products often need senior help that can fit into an existing codebase and delivery process without creating unnecessary churn.

What I did:

  • Provided targeted consulting around ecommerce/product delivery
  • Stepped into an existing ecommerce context for short, practical support
  • Focused on keeping the intervention scoped and useful rather than turning it into a rebuild

Tech: Ruby on Rails, ecommerce, consulting

Nexible

www.nexible.de

Production work on Nexible, Munich Re / ERGO’s digital-first insurance brand for online insurance journeys.

Problem: Digital insurance products need to make quoting, binding, managing, cancelling, and claims flows feel simple while still respecting complex insurance rules and operational constraints.

What I did:

  • Worked on product/backend delivery for Nexible’s online insurance experience
  • Supported digital customer journeys around policy management and claims-oriented workflows
  • Contributed inside a high-standard insurtech environment backed by Munich Re / ERGO

Tech: Ruby on Rails, insurtech, ecommerce-style funnels, production product development

Coverager: Nexible evolved beyond recognition · Branding reference

Panex / Hamburg Vaccination Center

www.hmc-annualreport2020.com/vaccination-center

Product/platform work connected to Panex and large-scale COVID vaccination-center operations.

Problem: Pandemic-era public-service operations needed appointment-driven flows, coordination, reporting, and reliable systems for high-volume vaccination logistics.

What I did:

  • Worked on software connected to vaccination-center operations and coordination
  • Supported workflows for large-scale, appointment-driven public-health logistics
  • Helped delivery in a context where reliability, clarity, and operational throughput mattered

Result: Public source context for the Hamburg vaccination center describes 64 vaccination lines, 7,000–10,000 daily capacity when supply allowed, and more than 2,000 employees involved.

Tech: Ruby on Rails, operational systems, appointment workflows, public-service logistics

Hamburg Messe annual report

Data ingestion system for SessionM, a customer engagement and loyalty platform later acquired by Mastercard.

Problem: Loyalty and personalization platforms depend on high-volume customer interaction data arriving reliably from many sources, with no room for silent data loss or fragile processing.

What I did:

  • Built Ruby/Rails-backed ingestion workflows for customer events, profile updates, and interaction data
  • Focused on reliability, validation, recovery, and data integrity across the processing pipeline
  • Helped support the infrastructure behind data-driven loyalty and personalization experiences

Result: A foundational ingestion system supporting SessionM’s customer engagement platform before its acquisition by Mastercard.

Tech: Ruby on Rails, PostgreSQL, Redis, data ingestion, customer engagement platforms

TwoMargins

www.twomargins.com

Collaborative financial research platform for annotating SEC filings and other complex financial and political documents.

Problem: SEC filings are large, irregular HTML documents that are difficult to parse, annotate, and integrate into partner workflows.

What I did:

  • Built the Rails backend and deployed the production infrastructure from scratch
  • Created a Nokogiri-powered parser for deeply nested SEC HTML documents
  • Integrated the annotation interface into external partner platforms
  • Supported product owners during peak-traffic document releases and U.S. election cycles
  • Onboarded and trained developers as the project matured

Tech: Ruby on Rails, PostgreSQL, Nokogiri

Wall Street Journal coverage

Cora

cora.com

Backend development support for an organic period and body care brand with ecommerce and subscription operations.

Problem: A growing D2C brand needed focused backend help inside an existing production product without disrupting existing workflows.

What I did:

  • Supported backend services behind product catalog, subscription management, and order processing
  • Stepped into an existing codebase for targeted delivery
  • Helped keep ecommerce operations moving for a mission-driven product team

Tech: Ruby on Rails, PostgreSQL

FanJolt

fanjolt.com

Fan engagement platform connecting audiences with celebrities and creators across sports, music, entertainment, and pop culture.

Problem: Consumer fan platforms need reliable product flows for live access, paid experiences, celebrity/talent management, and audience engagement without making the experience feel transactional.

What I did:

  • Worked on Ruby/Rails product development for a fan-to-celebrity engagement platform
  • Supported product flows around talent, fan interactions, and consumer-facing experiences
  • Brought practical experience from music/community products into a broader entertainment platform

Tech: Ruby on Rails, PostgreSQL, consumer product workflows, fan engagement platforms

Movieo.me

movieo.me

Movie discovery platform aggregating ratings and metadata from IMDB, Rotten Tomatoes, Metacritic, TMDB, OMDB, and other sources. Featured on Hacker News, Product Hunt, and Fast Company; used by 100,000+ people per month at its peak.

Problem: People needed a fast, pleasant way to discover what to watch across a large movie catalog with fragmented data sources.

What I did:

  • Built automated ingestion/update pipelines for 250,000+ movies
  • Designed caching and data delivery with Elastic and Redis for a fast user experience
  • Implemented advanced filtering and recommendation flows for movie discovery
  • Kept external API data synchronized and production-ready through background jobs

Result: A high-traffic, widely shared product with strong community reception and reliable daily data refreshes.

Tech: Ruby on Rails, PostgreSQL, Elastic, Redis, Thumbor

Fast Company coverage

Members-only fashion marketplace for women to exchange clothing and accessories, covered by Vogue and Crunchbase.

Problem: Fashion resale and closet-sharing products need to make inventory listing, discovery, social trust, and purchase flows feel editorial and community-driven rather than like a generic marketplace.

What I did:

  • Worked on product development for a consumer fashion marketplace
  • Supported marketplace-style flows around listings, profiles, discovery, and transactions
  • Brought production Ruby/product experience to a design-sensitive consumer ecommerce product

Tech: Ruby on Rails, marketplace workflows, consumer ecommerce, fashion/social commerce

Vogue coverage