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Julien Herr
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Hands-on CTO · EV-charging & critical B2B platforms

Hands-on CTO for EV-charging and critical B2B platforms.

I help EV-charging operators, SMEs and startups take over, harden or build their critical systems: OCPP, OCPI, monitoring, billing, ERP, architecture and delivery.

20+ years · from dev to CTO · Java / Kotlin / TypeScript · OCPP / OCPI · AI as a delivery accelerator · Strasbourg / Remote
CPO OCPP Roaming Supervision Platform Billing Smart charging SI / ERP
The through-line

Complex projects rarely fail on the technology. They fail when the business, the product and the code stop talking to each other. My job: get them moving in the same direction.

Primary focus: EV-charging operators and CPO / eMSP platforms. Then SMEs and startups with a critical B2B platform. AI, I use as a delivery accelerator — not as a separate promise.

Problems solved

What I know how to solve

01

Build a complex technical product

Turn a business idea, a regulatory constraint or an operational need into executable architecture, product and roadmap.

02

Take over an existing platform

Stabilise an architecture, reduce technical debt, clarify flows and get teams shipping again.

03

Bridge business and engineering

Translate the needs of operations, support, finance and product into features that are genuinely usable.

04

Structure a team or a transition

Act as interim CTO or Tech Lead, prepare a team handover, recruit, document and secure continuity.

Specialities

Three specialities, one way of working

E-mobility & energy

CPO and eMSP platforms, OCPP 1.6 and 2.x, OCPI and roaming, pricing, billing, monitoring, payment and IS integration — I master the whole chain, from the charge point to the usage.

OCPPOCPIRoamingCPO / eMSP

Engineering & leadership

From dev to CTO, via tech lead. Architecture (DDD, hexagonal, event-driven), legacy recovery, team structuring — and direct contribution on critical code.

Dev to CTODDDHexagonalLegacy

Accelerate delivery with AI

I use agentic AI to ship faster with smaller teams, without sacrificing quality — dev agents, framing, documentation and automation. A delivery multiplier, not a separate activity.

AgentsDeliveryUse casesTeams
Technologies JavaKotlinSpring BootTypeScriptPHPNestJSNuxtPostgreSQLMongoDBDockerCloudflareGitHub Actions
EV-charging value chain

From the charge point to the driver

I master every link in the charging chain: the charge point, the OCPP/OCPI protocols, CPO monitoring, roaming and eMSP-side usage — with proof.

See the full chain →
Featured projects

Platforms running in production

See all projects →
When to reach out

I can help if…

  • your platform works, but is becoming hard to evolve;
  • your business, billing or monitoring flows are not reliable enough;
  • your team ships slower because of technical debt;
  • you need to frame an OCPP / OCPI / billing / smart-charging product;
  • you need a hands-on CTO without hiring one right away;
  • you want to use AI to accelerate delivery without creating chaos.
Offers

Four ways to start

Indicative durations — tailored to your context.

Audit & recovery plan

Understand a platform, map the flows, identify the risks and produce an actionable 30/60/90 plan with quick wins.

5 to 10 days

Interim CTO / Tech Lead

Secure technical continuity, make the calls, structure the team, recruit and get delivery moving again.

1 to 3 days/week

Product & EV-charging architecture framing

Turn a CPO / eMSP / OCPP / OCPI / billing need into a target architecture and an MVP → production path.

Short engagement

Hands-on delivery

Ship or unblock a critical component in Java, Kotlin or TypeScript, accelerated by agentic AI.

Targeted engagement
Experience

20+ years building and recovering systems

See full experience →
Today

Independent CTO & Tech Lead

I support SMEs, startups and mobility operators on their critical platforms.

EV charging

Architect & tech lead

Designing and operating CSMS, eMSP portals and roaming integrations in production.

Product & legacy

Software architect

Recovering existing platforms and structuring delivery teams.

Engineering

Hands-on developer

Over 20 years writing production code, from the critical component to the overall architecture.

A product to build, a platform to take over, a team to structure?

Let's talk. Interim CTO, technical audit, product framing, EV charging expertise or development work.