Joanna Ionescu

S

Engineering Manager at Nokia · idempotency, Java

Nokia
Warsaw, Poland · CET (UTC+1)
10+ years experience
Sorbonne University
English, Polish
Co-founder
Messaging unavailable

Overview

I lead payments infrastructure at Nokia in Warsaw. Mentored 11 engineers through their first promotion. Designed the reconciliation system that matches 6 million transactions a day. Before that: Santander and Ericsson. Most at home with PCI DSS and gRPC.

Good reasons to reach out
  • People who want to build this with me
  • Thoughtful intros to people in my field
  • Second opinions on distributed systems decisions
Please don't message about
  • Courses and coaching offers
  • Agency or outsourcing pitches

Replies on weekday evenings

Skills
distributed systemsgRPCPCI DSSJavaidempotency
Co-founderLooking for a co-founder
closes in 3 months

Looking for a technical co-founder for cold-chain monitoring for mid-market retailers

The idea
Cold-chain monitoring for mid-market retailers
Stage
Customer interviews
I bring
8 years in payments infrastructure
Looking for
Technical co-founder who has shipped B2B software
Commitment
Full-time after funding
Location
Warsaw or remote

I bring 10 years of payments infrastructure (currently Nokia). Ideally you've shipped B2B software. Full-time from day one.

Warsaw, Polandjavaidempotencydistributed systems
Open

Experience

  1. Engineering Manager
    Sep 2024 - Present
    Nokia · 2 yr 1 mo · Full-time · Warsaw, Poland
    • Designed the reconciliation system that matches 9 million transactions a day.
    • Wrote the idempotency service that now handles 49 million requests a day.
  2. Backend Engineer
    Apr 2022 - Sep 2024
    Santander · 2 yr 5 mo · Full-time · Warsaw, Poland
    • Shipped a rewrite that took build times from 24 minutes to under 2.
  3. Senior Backend Engineer
    May 2020 - Apr 2022
    Ericsson · 1 yr 11 mo · Full-time · Warsaw, Poland
    • Wrote the distributed systems service that now handles 41 million requests a day.
  4. Backend Engineer
    Jun 2017 - May 2020
    ING · 2 yr 11 mo · Full-time · Warsaw, Poland
    • Shipped 18 launches on the payments platform team without a rollback.
  5. Backend Engineer
    Oct 2016 - Jun 2017
    BlaBlaCar · 8 mo · Full-time · Warsaw, Poland
    • Cut p99 latency on the payments platform services from 680ms to 174ms.
    • Shipped a rewrite that took build times from 37 minutes to under 3.

Projects

Open-source gRPC toolkit
2025

A small library for payments infrastructure that 376 developers star on GitHub.

Write-up: payments infrastructure in practice
2025

A long-form guide to payments infrastructure for people starting out.

References

No references yet.

Education

  1. Sorbonne University
    Licence, Electrical Engineering
    2012 - 2015

Details

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