Backend Python Engineer

Senior Full-Stack Engineer (Python / High Concurrency Systems) — CDMX

cold.email is one of the fastest-growing cold email marketing agencies in the world.

We’ve 5×’d in size since January and continue to scale rapidly. 30k USD MRR - 140k USD MRR

Learn more at cold.email

or on youtube.com/@johntannerworthington

About Us We’re a cold email agency — a type of lead generation company. We act as an outsourced outbound marketing team for our clients.

Example: Suppose you sell supplements to doctors.

We will:

Scrape Google Maps to identify all the doctor offices in the U.S.

Extract company details and contact info from each site (e.g. estimating@aaapaving.com).

Match each business to decision-makers using LinkedIn datasets (via APIs like Icypeas.com).

Brute-force and verify email addresses using APIs like Findymail.com.

Send at scale via Instantly.ai, manage responses, and deliver qualified leads to clients.

In short, we build our own data pipelines to generate leads from scratch, at scale.

Role Overview

You’ll build and maintain the custom software infrastructure that powers our growth — from scrapers and enrichment systems to analytics dashboards.

Projects you’ll work on:

Large-scale web scrapers for Google Maps and Google Search (millions of listings per month).

Async API infrastructure (FastAPI + aiohttp) deployed to AWS Lambda or Render.

AI pipelines using OpenAI for fuzzy matching, classification, and web analysis.

Distributed streaming systems (Celery + Redis) to process millions of enrichment tasks per day.

Internal dashboards that aggregate analytics from tools like Instantly.ai, Serper.dev, and our proprietary APIs.

Qualifications

Deep experience in

Python

, especially async programming (aiohttp, asyncio, httpx).

Proven ability to manage

very high QPS (1000–1500/sec)

API pipelines.

Experience deploying to

AWS Lambda

,

Render

, or similar cloud platforms.

Strong with

Postgres / Supabase

for structured data storage.

Celery / Redis

experience for distributed queues and streaming pipelines.

Fluent or native-level

English

(written and spoken).

Ability to work

on-site in CDMX

(hybrid acceptable).

Cold email or marketing experience is not required.

We need a world-class builder who can design stable, efficient systems.

Compensation \& Benefits

MX$60,000 - MX$200,000 / month depending on experience

Full-time employment with benefits and PTO

Insurance

Company offsites and rapid career growth opportunities

Stock options

Example APIs We Use

Serper.dev Structured data from Google Maps and Search

Instantly.ai Campaign and lead data

Icypeas.com LinkedIn dataset of 200M+ profiles

OpenAI For fuzzy matching, classification, and text analysis

Why This Role Matters

We’re building one of the most technically advanced outbound systems in the world.

Your work will power millions of API calls, billions of data points, and the backend of an agency scaling faster than almost anyone in the space.

I am a technical product manager, but not a software engineer. I will need someone who can work with me directly and help me build the vision of these products, as they fit our client needs. I have built MVP's in no code tools, as well as vibe coded slop, but its not at the point where we can scale stabley given our growth.

I am based in Mexico City, and am looking for someone to work closely with in person, and then move to hybrid or fully remote. I do speak Spanish, conversational level, not fluent, so we do need a near fluent speaker who can write code in English.