case-study200 OK · 400K DAU
Enterprise Two-Factor Authentication
Designed and implemented a scalable 2FA platform serving 300K–400K daily active users across Jotform’s enterprise and consumer products.
system status: operational — Nuremberg, Germany
Mustafa Culban
$
I build scalable B2B SaaS platforms with a strong focus on backend architecture, security, and cloud infrastructure. I enjoy owning critical systems end-to-end and turning complex requirements into reliable production software.
8+
years shipping SaaS
400K+
daily active users served
20TB
traffic in one broadcast
6
engineers hired & mentored
$ try:
How I engineer
// principles.md01
Own it end-to-end
Design → implementation → rollout → iteration. Systems are only done when they survive production, and then only until the next incident.
02
Security is a feature
2FA for 400K users, OAuth2 migrations, SOC 2 and GDPR compliance. Trust is the real product; everything else is UI.
03
Measure, then brag
Latency from 400ms to 250ms. Account takeovers down 15%. First-touch time down 25%. If it is not measured, it did not happen.
04
People scale systems
Five direct reports, 30+ technical interviews, 24 interns mentored. The best architecture decision is often a hiring decision.
contribution.log
GitHub activity
$ fetch contributions --year last
Career, version-controlled
// career.git➜ career git log --oneline --graph
* f7c2026 (HEAD -> main, tag: v2026) status: open to senior backend/full-stack roles — Nuremberg, Germany
* e91a5d3 chore(jotform): hand over 400K-DAU systems after 7+ years — 2026-05
| * b4e91c2 (devjoys) feat(metrajai): AI-assisted quantity workflow — in development
| * d17a30f feat(bananeresi): conditional relocation analysis + resumable questionnaire
| * e62c8ab feat(vefuno-fit): branch-scoped gym memberships + scan-time access
| * 9f3d14c feat(vefuno): digital loyalty flows — QR/NFC + wallet architecture
| * 5a8e27d feat(velora): dimensional scoring + archetype results — in development
| * 7c1b90e feat(medreseai): gamified learning loop — in development
| * c8b41f2 feat(jurispy): AI verdicts live — web + App Store
| * a730e9c feat(dronefleethq): 8 paying customers · ~$240 MRR
| * 94d2c1b feat(tande): launch on the iOS App Store
| * 81f6a4e init(devjoys): one-person AI product studio — 2024-01
|/
* 7325bd9 feat(smtp): OAuth2 modernization — zero-downtime rollout
* 6ab90e4 feat(growth): CRM analyzing 15–20M users — first-touch time -25%
* 61de4a8 feat(teams): multi-tenant workspaces + centralized RBAC
* 58c17df feat(auth): 2FA for 400,000 daily users — SOC 2 & GDPR
* 4f02b8a chore(team): hire 6 engineers · mentor 24 interns
* 3d91c56 feat(jotform): join as senior engineer → team lead — 2019-01
* 2c80ea7 feat(anvato): 20TB Super Bowl live-stream window — 2018
* 1b7f9d3 init: B.S. Computer Science @ Bilkent University — 2013
Selected work
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productLIVE
Bananeresi
Personalized relocation analysis product built around conditional questionnaires, resumable state, structured pathway analysis, and country-specific guidance.