Midlevel / Senior Back End Engineer (Laravel)

About Carno Carno is a fast-growing climate tech startup building the operating system for the UK's renewable energy installation industry. Our platform streamlines surveys, design, quoting, and compliance workflows for renewable installers, cutting admin time by up to 90%. We're backed by industry partners and already powering thousands of heat pump installations across the UK. Our mission is to accelerate home decarbonisation at scale by empowering installers with world-class software.

Role Overview We're hiring a Senior Backend Engineer (Laravel) to take real ownership of our Laravel microservices platform. You'll build the architecture that powers a scientific calculation engine, multi-tenant data layer, external data integrations, and the compliance framework that certified installers depend on daily.

You'll work closely with our CTO, and the wider engineering team, shipping backend infrastructure that directly shapes how our platform operates at scale.

We need someone who thinks beyond the ticket in front of them, understanding how decisions around service boundaries, package architecture, and data isolation compound over time as the platform grows.

This is a hands‑on engineering role with significant ownership and direct influence on the product.

Key Responsibilities

Build and maintain multi‑tenant SaaS architecture with strict tenant isolation, scoped data layers, and customisable business logic per organisation

Own and extend our scientific calculation engine, which models building thermodynamics, sizes heating systems, and assesses regulatory compliance

Develop and version shared internal Composer packages consumed across all Laravel microservices

Build and maintain integrations with third‑party property data APIs and external data sources

Work on authentication and authorisation systems supporting OAuth 2.1, RBAC, SSO, and organisation‑based access control

Design and maintain async queue pipelines for complex chained background processing

Work across CI/CD pipelines managing coordinated releases across multiple repositories

Implement and maintain event‑driven patterns using observers and Redis pub/sub

Collaborate with product, design, and engineering in an agile environment

Contribute to new backend architecture as we expand into new energy segments and platform capabilities

Design and maintain inbound and outbound webhook systems, including event delivery, retry/backoff strategies, and idempotent processing

What You’ll Experience at Carno

Flexible, hybrid role with adaptable hours and occasional in‑person collaboration at our Blackfriars HQ

Direct collaboration with CTO, CEO, and CPO

Fast‑moving environment where your work ships quickly and impacts installers immediately

High ownership of platform architecture, with autonomy to shape technical direction

A supportive team that values transparency, feedback, and continuous improvement

Candidate Requirements

5+ years in Laravel (PHP) in a professional engineering environment

Multi‑tenant SaaS or PaaS architecture – tenant isolation, scoped databases, cross‑tenant query patterns, and shared‑state pitfalls

Strong computer science and mathematics fundamentals – able to implement thermodynamic and energy efficiency formulas, interpolation algorithms, and recursive dependency logic

OAuth 2.1 – client credentials and authorisation code flows, token management, scopes, and modern identity platforms

Elasticsearch – indexing strategies, query DSL, and application‑level integration

Docker for local development and multi‑container orchestration

CI/CD pipelines – automated testing, linting, and deployment across multiple repositories

Event‑driven architecture – observers and Redis pub/sub

Strong security foundation – input validation, authorisation boundaries, secret management, OWASP/CVE awareness

Webhook integration patterns – signature verification, HMAC‑based payload signing, replay attack prevention, and reliable delivery guarantees

Preferred Technical Skills

Python (FastAPI or Django), particularly for services running alongside Laravel

LLM and generative AI integration

Webhook systems: designing, signing, delivering, and retrying outbound events

Heat pump, solar, or renewable energy industry knowledge (MCS, SAP, EPC, building physics)

Soft Skills

Strong analytical mindset with the ability to reason through complex, interconnected systems

Clear communicator who can work across engineering, product, and compliance domains

Thrives in a startup environment: adaptable, reliable, and intellectually curious

Commitment to correctness and code quality in a platform where precision matters

Ability to see the bigger picture and understand how backend architecture decisions affect the entire product

Experience 5+ years in Laravel (PHP) with strong fundamentals across distributed systems, multi‑tenant architecture, and scientific or calculation‑heavy backend engineering.

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