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Mathew Joseph

I help founders move beyond referral-only pipeline by building outbound systems their teams own and run

LondonLinkedIn

GTM engineer since 2024: outbound systems for B2B teams as a freelancer, then for RevenueFlow's clients. Since June 2025, as GTM engineer at Cerebrium, a YC-backed AI infrastructure company, I have built its go-to-market system from nothing: enrichment and qualification in Clay, HubSpot beneath it and the outbound on top. Its CEO has publicly cited a 55% LinkedIn reply rate against a 2-4% norm.

1Cohort finished, every submission gradedFrom Clay
4Builds shippedFrom Clay
39Classmates helped, marked by themFrom Clay
2Clay certificationsFrom Clay

25/25

Clay Solutions Partner exam

Mathew's number

$100K

new MRR into pipeline, per CEO

Mathew's number

55%

LinkedIn reply rate vs 2-4% norm

Mathew's number

Work

Reviewed inside a cohort where it says so. Numbers are the student's.
Case study
Cerebrium, embedded GTM engineer, since June 2025
An outbound pipeline from sources to CRM
Pulls potential customers from several sources, screens them against the company's own criteria in Clay, enriches the ones that qualify and routes them into HubSpot. It replaced prospecting by hand; the commercial team has run on it since 2025. Tradeoff: cheap screening runs before paid enrichment. Broad filters give a weaker signal, but no company that gets rejected costs an enrichment.
Case study
Cerebrium, 2026, outside my assigned role
Cerebrium's official agent toolkit for AI coding assistants
Developers ask AI coding assistants to set up their deployments, and leave quietly when it breaks. I proved with a reproducible test that the file those assistants read failed its own spec, then specified, directed and shipped the fix and an official toolkit, executing through an AI coding agent. Tradeoff: directing an agent made it fast, so a second reviewer approved every change before merge.
Case study
Cerebrium, July 2025 to April 2026
A reply standard that became an automated classifier
In my third week I wrote the standard for answering interested prospects: answer directly, give one piece of proof, offer a low-friction next step. When volume outgrew human reading, I designed a classifier that checks each conversation against the ICP and records every decision. Tradeoff: it reads the whole thread, not reply 1, at extra cost, as a contact can sound keen and then close the door.
Case study
Cerebrium, August to September 2025
A lead-source model, tested and reversed
One practitioner's LinkedIn audience was converting to meetings noticeably better than the rest, and nobody knew why. I turned it into a model of what makes a source worth monitoring, and set up a record linking meetings to their source campaign. Within a month it showed my top-ranked source had booked none, so I reversed the model. Tradeoff: a model can fail where a list cannot; I chose that.
Case study
Cerebrium, January 2026
One version-controlled source of truth for GTM
With two separately built GTM frameworks in play, I moved 100+ GTM documents into version control in one operation, added a source-of-truth register and an append-only decision log, then merged both frameworks into one customer definition. Tradeoff: I accepted a reversal of my own design, screening on company data before the costly signal work, because screening cheaply first was better.

Skill map

4 Clay use cases proven, 3 shared. Tap or hover one to see the proof and what it is built from.
Proof levelsCertified by ClayVerified workShared, in review
Phase 1

Crawl

Clean, scored data you can trust

1 proven, 2 shared
Phase 2

Walk

Automations that run without you

2 proven
Phase 3

Run

Signals and reps working the same system

1 proven, 1 shared

Data foundation

Reachable accounts and contacts, lower tool spend

Crawl

Grow pipeline

Outreach volume, reply rate and speed to lead

Walk
Run

Building blocks

22 proven. The Clay skills every use case is made of. Tap or hover a use case to see its recipe.

Sourcing4Where records come from
Enrichment4What you learn about them
Logic8What you decide
Activation3Where the decision lands
Operate3Why it keeps working

Credentials

Issued by Clay. Anyone can verify the ID.

Automated Inbound

A real build, a walkthrough and an interview, reviewed by Clay
Nov 2026 · CC-SK-B7EF37ECVerify
0.02% of the Clay community hold this

Outbound Orchestration Foundations Cohort 5 diplomaOutbound Foundations

Cohort completed, every submission graded
Nov 2026 · CC-DIP-F544F528Verify
0.31% of the Clay community hold this

Outbound Automation

A real build, a walkthrough and an interview, reviewed by Clay
Oct 2026 · CC-SK-1FD17AAEVerify
0.03% of the Clay community hold this

Teams I've built for

Skills

Levels come from graded work and certifications, not self-report
Automated InboundExpert
Outbound AutomationExpert
Outbound Orchestration FoundationsAdvanced
Clay 101: GTM AutomationWorking

Journey

Earned the Automated Inbound
Certification
Nov 2026
Graduated Outbound Orchestration Foundations Cohort 5
Diploma earned
Nov 2026
Returning student
Came back for another cohort
Nov 2026
Earned the Outbound Automation
Certification
Oct 2026
First reply
Answered a classmate
Oct 2026
Joined Outbound Orchestration Foundations Cohort 5
Outbound Orchestration Foundations
Oct 2026
Joined Clay 101: GTM Automation
Clay Cohorts
Oct 2026
Credentials and badges are issued by Clay. Mathew can hide them, not edit them.