GTM systems & MarTech developer · Lisbon

Less busywork.
More business.

I build apps, integrations, and AI tools that help sales and marketing teams find prospects, use their data, and automate manual work.

I'm Oscar Tellez, a developer who has worked in sales, managed Google Ads and Meta campaigns, and run a business. I turn the day-to-day problems of go-to-market (GTM) teams into working software.

Discuss a project Explore my work

Hiring? Download my CV

40,000+European e-commerce sites scraped
and enriched for sales prospecting

Business context. Technical execution.

Oscar Tellez, MarTech developer based in Lisbon

Oscar TellezGTM systems & MarTech developer

Python · JavaScript · Google Cloud

Experience spanning
development & commercial teams

Google ^{via Algomarketing}Developer & Delegate Activation Manager

Growth HorizonMarketing Automation Developer

PriceShapeBusiness Development Representative

01 / Flagship projects

Real problems.
Working solutions.

Each project starts with a business problem: billing that needs custom rules, disconnected customer data, or sales information that's hard to use.

01Featured / Agency revenue operations

Revenue OS.

Billing built around client performance.

A marketing agency I worked for bills clients on performance, with different terms for each client. Standard billing systems couldn't handle that model, so I built Revenue OS.

It pulls performance data from Klaviyo, applies each client's billing terms, and generates invoices, performance reports, and email drafts ready to send.

Softphone data brings sales activity into the same workspace. Sellers can track their commissions, which also depend on each client's performance.

Ozzie, the built-in AI assistant, can answer questions using operational and financial data, help troubleshoot errors, and generate invoices.

What it changes

Client results become the basis for billing and commission tracking, with reports and draft emails prepared in the same app.

Full-stack application
Klaviyo · Gmail · Adversus
Performance-based billing

Ask me about Revenue OS

Earlier Revenue OS interface showing the agency dashboard, invoicing navigation, and Ozzie assistant, with client identifiers redacted — Earlier app interface with client identifiers redacted. View larger

Redacted growth-metrics interface showing order revenue, Google Ads, Meta, channel reporting, and data-quality views — growth-metrics · redacted app view

02Personal project / Webshop pilots

growth-metrics.
Investigate missing conversions.

As a paid ads manager, I faced gaps in Google Ads and Meta conversion reporting. That experience was one reason I built growth-metrics with my own server-side tracking to compare captured conversion data with platform reports.

It's my personal project, currently being piloted with a few webshops. The app brings server-side measurement, order revenue, and Google Ads, Meta, and Klaviyo reporting into one workspace. Data-quality checks help make gaps visible.

Early pilot observation: in these webshops, Google Ads has consistently reported roughly half the return on ad spend (ROAS) shown by my server-side data.

Server-side tracking
Google Ads · Meta
Klaviyo
Data quality

Ask me about growth-metrics

FROM CONVERSATIONS TO CONTEXT

Sales callsTranscriptsAI agent

03Applied AI / Sales-call knowledge

Find the detail.
Skip the replay.

Preparing a follow-up shouldn't mean replaying an entire sales call. I built a system that fetches softphone recordings, transcribes them locally (no API costs) with Whisper, separates speakers, and creates summaries using Gemma 4.

I connected a Hermes agent to the transcription database so teams can ask questions about past calls through Telegram. I developed the system locally and deployed it on a separate remote PC.

What it enables: retrieve call details and follow-up context by asking a question.

Local transcription
Hermes agent
Telegram

Ask me about this workflow

04API engineering / Growth Horizon

Opening Klaviyo
to more webshops.

Missing connectors kept some webshops out of reach for the agency's Klaviyo services. I built connectors for Lightspeed, Mijnwebwinkel, and Logic4 that weren't available at the time.

The connectors import customer history and synchronize new events and store activity with Klaviyo, enabling those stores to run email marketing workflows.

What it changed: the agency could offer Klaviyo to more stores, expanding the potential client base for both the agency and Klaviyo.

Python
REST APIs
Google Cloud
JavaScript

Have an integration challenge?

05Data engineering / Sales prospecting

40,000+ sites.
Research that shaped the offer.

I built multi-source scraping and enrichment workflows to find e-commerce prospects that fit the agency's target customer profile. Covering 40,000+ European e-commerce sites, the system checked for e-commerce activity and identified each store's platform (CMS), email marketing tools, and relevant contact information.

CMS data helped prioritize stores that connected easily to Klaviyo. Knowing which email marketing tool a store used also helped cold callers prepare before reaching out.

Being able to identify stores on platforms without a native Klaviyo connector helped the agency target its custom integration offering. Lightspeed was one example at the time.

What it changed: one dataset guided prospect selection, outreach segmentation, and a custom integration offering that differentiated the agency.

Python
Node.js
Data enrichment

Let's talk about your data

Much of my work lives inside private business systems. Happy to discuss the architecture, decisions, and implementation in a conversation.

02 / How I help

Where is your team
losing time?

I build around the work your team needs to do: qualify prospects, follow up, measure results, and bill clients.

“Our tools don't talk to each other.”

Connect your stack.

Custom API integrations and data pipelines that keep your CRM, softphone, marketing platforms, and business systems in sync.

Python · REST APIs · Google Cloud

“Our sales team is buried in admin.”

Automate sales operations.

From prospect enrichment and CRM workflows to onboarding and invoicing, I automate the manual work around your sales process.

Apps Script · JavaScript · n8n

“We have data. We need answers.”

Make information useful.

Dashboards and AI agents for outreach performance, sales-call knowledge, and marketing results, so teams can ask questions, find answers, and act on their data.

SQL · BigQuery · Looker Studio · AI

Tell me what's slowing you down

03 / The person behind the systems

From doing the work
to building the tools.

I've worked in sales and digital marketing, including managing paid campaigns on Google Ads and Meta. I've also handled procurement and business operations.

The reporting challenges I faced as a paid ads manager were one reason I built growth-metrics. I wanted a clearer view of conversions than platform reports alone could provide.

In sales, I booked appointments across European markets and used outreach data to improve follow-up. As a hospitality business co-owner, I handled bookkeeping, budgets, payroll, and front-of-house operations.

That background shapes how I build. I start with the task and the business rules, then connect the data and tools needed to make it work. Revenue OS grew out of exactly that approach: turn a complex billing model into software the agency can use.

Today, I work in Algomarketing's Center of Evolution (COE) for Google in Lisbon, supporting Google Germany across the DACH region. My role combines development with event audience and delegate activation work.

Download my CV LinkedIn

Native Spanish · Fluent English · Learning Portuguese

May 2026 — Present Current

Google ^{via Algomarketing}

Developer & Delegate Activation Manager

Based at Algomarketing's Center of Evolution (COE) for Google in Lisbon, I support Google Germany's event and delegate activation work across DACH (Germany, Austria, and Switzerland). I build Apps Script workflows, data pipelines, and internal apps to validate and synchronize attendee data. I also manage audience segmentation and automate reporting so teams can work with consistent event data.

Dec 2024 — May 2026

Growth Horizon

Marketing Automation Developer

Built previously unavailable connectors between Klaviyo and Lightspeed, Mijnwebwinkel, and Logic4. This enabled the agency to offer Klaviyo to more stores, expanding the potential client base for both the agency and Klaviyo. Developed sales intelligence pipelines, Google Cloud automations, and internal business applications.

May 2024 — May 2025

PriceShape

Business Development Representative

Booked appointments across Northern Europe and Spain in English and Spanish. Used outreach data to refine follow-up, and built Looker Studio dashboards to track lead quality, hit rates, and no-shows. Improved prospect data and automated softphone reporting for lead forecasting. The COO estimated the reporting automation saved four months of manual quality checks.

Business foundations. Technical depth.

M.Mgmt. in Agribusiness, Lincoln University (Merit) · B.Sc. in Finance, Universidad Americana

Certifications & continued learning

Agentic AI
Generative AI Leader Certification
Gemini for Google Cloud Learning Path
BigQuery for Data Analysts
Creating Business Value with Data and Looker
Applied Data Science Lab
Computer Science Career Path
Google Advanced Data Analytics Certificate
Data Analyst Professional Certification

04 / Let's build something useful

What's the thing
you wish just
worked?

Prospecting that takes too long, customer data stuck in separate tools, or billing rules your software can't handle. Tell me where the work gets stuck and what you need to change.

WhatsApp ↗LinkedIn ↗

Hiring for GTM systems, MarTech development, or automation?
Get the full CV

Less busywork.More business.

Real problems.Working solutions.

Revenue OS.

growth-metrics.Investigate missing conversions.

Find the detail.Skip the replay.

Opening Klaviyoto more webshops.

40,000+ sites.Research that shaped the offer.

Where is your teamlosing time?