Midlevel / Senior Back End Engineer (Laravel)

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Carno

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London, United Kingdom

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Senior Backend Engineer (Laravel) — Carno


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
  • AWS - EC2, RDS, Elasticache, S3, Application Load Balancers
  • 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
  • Document generation (OOXML, PDF rendering, template-based composition)
  • 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.