HI, I'M

Yusuf Erkan Darıyemez

Senior Software Engineer

I build scalable backend systems with Go and PostgreSQL — payment flows, integrations and data-heavy production applications.

Yusuf Erkan Darıyemez
6+years building production systems
50+projects built to date
17open source repos
Go · PostgreSQLcore stack

About

I'm a senior backend developer with six years of production experience, almost all of it in Go and PostgreSQL. I've designed and built the backend architecture of ERP, CRM, donation-management, accounting and payment systems, established team-wide engineering standards, and led a seven-person cross-functional team through mentoring and code review.

The systems I build move real money and real data: payment provider integrations, accounting and reconciliation flows, multi-tenant platforms, audit trails, and the reporting paths on top of them. My bias is correctness first — explicit code, layered architecture, carefully modeled schemas, and query performance that is measured rather than guessed.

On the side I maintain open source Go libraries and tools, extracted from patterns I kept rebuilding at work — including standalone guards for the parts of operations nobody usually watches: query plans, data freshness, webhook delivery.

What I do

Backend systems & APIs

RESTful APIs, background jobs, third-party integrations with idempotency and retry discipline.

Money & correctness

Payment flows, double-entry accounting, bank reconciliation — no floats near money, everything provable.

PostgreSQL reliability

Query plan regressions, data freshness, integrity — tools that catch problems in CI, not at 3 AM.

Flagship product

live, in production

yokla

Technical Interview Simulation Platform
Founder & Engineer LIVE

A technical interview simulation you enter by picking seniority × field × specialization — then get scored and benchmarked.

Pick seniority × field × specialization, take a scored MCQ interview, and see where you land against everyone else — with progress tracking, practice mode and an optional AI coaching report. 25,000+ questions were AI-generated and put through a multi-layered, independent verification pipeline; the product itself has no runtime LLM dependency (MCQ + deterministic scoring, $0 runtime cost). I designed and built it end to end: architecture, backend, frontend, data model and deployment.

  • Go 1.25 / Echo v5
  • raw pgx (no ORM)
  • PostgreSQL 18
  • Nuxt 4 SSR / Vue 3
  • Pinia
  • Tailwind v4
  • Voyage AI embeddings
  • Gemini Flash-Lite
  • Claude Haiku
  • Docker Swarm
  • GitHub Actions CI
  • nginx + Cloudflare
  • Prometheus + Grafana
  • AI content generation plus independent verification: parallel generation forks → programmatic scans (language, "longest option" tell, topic alignment) → independent auditor + adjudication. Generation/verification on a cheap model, only adjudication on a strong one → ~4-5× cost cut.
  • "Postgres-first, measure before adding": pgvector and Redis were rejected after measurement (cosine scan runs in seconds in Go, latency is RTT-bound). No needless production risk taken.
  • One dataset, three uses: embeddings built with Voyage AI → dedup + in-interview diversity guard (1.7% unfiltered → 0/300 filtered) + topic auditing.
  • JD → interview: embedding collapsed on job-post matching (.NET → devops); a provider-agnostic design let one adapter swap move it to a Gemini Flash-Lite classifier (~$0.00024/post); taxonomy is read from the DB → a new field means zero code.
  • Optional AI coaching report (Claude Haiku): cached per (user, locale), every real call logs tokens + cost → ~$0.002/report; the feature turns off silently when no key is set.
  • In progress: a verifiable yokla score — a shareable, independently checkable result credential.

yokla.dev ↗

Open source

selected work

All repositories on GitHub →

Writing

Production war stories — distributed locks that weren't, event buses that lost messages, floats that touched money. Mostly Turkish, some English.

All posts on Medium →

Building a system?

Write me about backend architecture, payment infrastructure or PostgreSQL.

yusuf.erkamyed@gmail.com