CASE 02 / Product & systems
Building the backend for EV charging.
At Numocity, I owned the OCPP server for 20k+ charge points worldwide and architected an aggregator for multiple charging operators.
- THE PROJECT
- Behind the charge
- THE CONTEXT
- Numocity
- THE CHAPTER
- 2023 - 2025
- THE PROBLEM
- Connect physical chargers and multiple charging operators to one wider platform.
- WHAT I OWNED
- OCPP server ownership, operator aggregator design, load-testing tools, and production incident response.
- THE RESULT
- Backend development for 20k+ charge points worldwide, plus an aggregator connecting multiple operators.
Original concept illustration, not a production screenshot. Internal product details are intentionally kept high-level.
COMPONENTS / RESPONSIBILITIES / SCOPE
How the parts fit together.
A guide to the areas I worked on at Numocity. The disconnect and settlement scenario in the linked lab is a separate simulation, not a reconstruction of a production incident.
01
Charger connection
My OCPP work used persistent WebSocket connections between chargers and the platform.
- The boundary
- This is the device-facing part of the platform, separate from integrations between operators.
- Implementation note
- I also built a charger simulator during my internship so demos and testing did not always require a physical device.
02
OCPP server
I owned this repository, developed features, refactored code, and reviewed changes.
- The boundary
- Repository ownership was one part of a wider team-built charging platform.
- Implementation note
- My responsibilities included production incidents and load-testing work, not only new endpoints.
03
Operator aggregator
I built a microservice that integrated multiple charging operators.
- The boundary
- Operator integration and charger protocol handling were separate pieces of my work.
- Implementation note
- This summary does not claim that all operators exposed identical behavior or that I authored the wider platform.
04
Business services
I also worked on authentication, subscriptions, payments, invoicing, and reporting.
- The boundary
- Those services sit alongside the charger and operator integrations.
- Implementation note
- The linked lab isolates one billing scenario with fictional data; it does not reproduce these services.
Conceptual responsibility map. Not a production deployment diagram or a screenshot.
01 / The problem.
The charging platform had two integration problems: communicating with physical chargers over OCPP, and connecting multiple charging operators. I worked on both the charger-facing server and the operator aggregator, alongside the services for subscriptions, payments, invoicing, and reporting.
02 / My role.
At Numocity, I designed EV charging microservices for real-time charger-to-CSMS communication over WebSockets and owned the OCPP server managing 20k+ charge points worldwide. I architected an aggregator for multiple charging operators and built OTP authentication, subscription, payment, invoicing, and reporting modules for a platform serving 10+ Fortune 500 clients. I also developed load-testing tools and served as a Site Reliability Engineer, resolving critical production incidents.
- My contribution
- Owned the OCPP server for 20k+ charge points, led features and code reviews, and architected the charging-operator aggregator.
- Shared scope
- The platform served 10+ Fortune 500 clients. I built modules and handled site reliability within that wider team-built platform; its customer reach is not a claim of sole authorship.
- What changed
- An operator aggregator, continued OCPP server development, and load-testing tools.
03 / Implementation details.
- Maintaining the OCPP server while adding features and reviewing changes.
- Integrating multiple Charge Point Operators into an aggregator microservice.
- Building load-testing tools and investigating production incidents alongside feature work.
04 / The result.
- Unified multiple charging operators behind an aggregator microservice.
- Led OCPP server features, refactoring, and code reviews for 20k+ charge points worldwide.
- Built load-testing tools and resolved production incidents.
- Developed an OCPP-compliant charging simulator during my internship.