Senior Software Engineer · Istanbul
Serkan Demir
I build backend systems that scale, mostly in Go, Kotlin, and Java. After banking and telecom, I'm now building fintech products at Trendyol.
“Not all those who wander are lost.”
About
An unexpected journey into software
I started my career in 2018 on the mainframes of a bank, writing COBOL next to engineers who'd been doing it for decades. It taught me that reliable software is mostly about understanding the business it serves.
Since then I've moved through telecom and into e-commerce and fintech, trading mainframes for microservices along the way. Today I work on backend services in Go, Kotlin, and Java, and I care about systems that stay simple, observable, and fast under real traffic.
Outside of work, you'll probably find me rewatching The Lord of the Rings for the hundredth time.
- Years building software
- 8+
- Industries
- 3
- Rewatches of The Lord of the Rings
- ∞
Journey
The road goes ever on
Three companies, three industries, one thread: building software people rely on every day.
Trendyol
Senior Software Engineer · E-commerce and fintech
2022 — Present
Three teams so far: seller financing, international growth, and now TrendPay, Trendyol's digital wallet.
- Wallet User (current): own login, registration, authentication, and every other user-facing flow in TrendPay
- Engagement Products: built products that bring shoppers on Trendyol's international storefronts into the mobile app and turn app usage into a habit
- Seller Finance: integrated with partner banks so sellers could access loans at favorable interest rates
- Kotlin
- Go
- Java
- Couchbase
- Elasticsearch
- PostgreSQL
- Grafana
- GitLab
Vodafone
Software Engineer · Telecommunications
2020 — 2022
Member of the TOBi squad, working on the chatbot embedded as a web view inside the Vodafone mobile app.
- Built microservices with Spring Boot on Red Hat OpenShift
- Contributed to the React front end of the chatbot web view
- Java
- Spring Boot
- React
- OpenShift
- Microservices
Garanti BBVA
Software Engineer · Investment banking
2018 — 2020
Where the journey began: on the Investment Banking team, learning banking systems and business processes alongside experienced engineers.
- Developed and maintained investment banking applications in COBOL and CA Gen (Cool:Gen)
- Learned the business processes behind large-scale financial systems
- COBOL
- Cool:Gen
- Mainframe
Stack
Tools of the craft
What I reach for day to day.
Languages & frameworks
- Go
- Kotlin
- Java
- Spring Boot
- React
Data & messaging
- PostgreSQL
- Couchbase
- Elasticsearch
- Kafka
Infrastructure & delivery
- Docker
- Kubernetes
- OpenShift
- GitLab
Observability
- Grafana
- New Relic
- Dynatrace
- Kibana
Contact
Speak, friend, and enter
Whether it's a role, a project, or a chat about backend engineering or Middle-earth, my inbox is open.