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hekimcan206/README.md

Hekimcan Aktaş: software engineer working on systems where correctness, privacy and auditability are requirements.

I build backend and data systems for places where a wrong answer is expensive: money that must balance, health records that must stay private, and regulations that must be enforced in code rather than in a policy PDF.

My method is the same in every repository. I name the invariant, find the failure that would break it, prove it holds with a test against a real database, then measure the cost and write down the trade-off.

Website Email

Selected work

ledger-recon
PostgreSQL · .NET 10 · FsCheck · NBomber

A double-entry ledger with exactly-once posting and end-of-day reconciliation against card, EFT/FAST and MT940 files.

50 concurrent duplicates → 1 entry
1,185 RPS · p99 75.9 ms

medula-precheck
Oracle 23ai · PL/SQL · .NET 10

Healthcare billing rules as versioned, effective-dated code, with a set-based PL/SQL bulk path that matches the .NET engine finding for finding.

22 rules × 3 versions
byte-identical on 3,000 invoices

kvkk-data-inventory
Oracle · PostgreSQL · KVKK / GDPR

Finds, classifies and masks personal data across two database engines. Masking is keyed and one-way, and preserves checksums.

F1 0.939 on a labelled schema
2,079 columns scanned in 0.94 s

dotnet-service-template
.NET 10 · OpenTelemetry · Testcontainers

The baseline every service starts from, installed with dotnet new hekim-service. It includes analyzers as errors, a chiseled non-root image, CI and CodeQL.

198 MB image · ready in 10.4 s
93.7% line coverage

Every number above comes from a reproducible run. Each repository's docs/benchmarks.md records the hardware, the host load and the method.

Engineering principles

Invariants live in the database. Deferred constraint triggers, append-only history and least-privilege roles. Application code is a second line of defence, not the first.

Tests attack, they don't confirm. Property-based tests, concurrency races and golden cases all run against real PostgreSQL and Oracle through Testcontainers.

Numbers or it didn't happen. A performance claim ships with its benchmark, its environment and its outliers.

Decisions are written. Every repository has ADRs listing the options I rejected and why, plus an honest Limitations section.

Privacy is a design input. Before a schema exists, I decide who can see the data, how long it lives and what trace an access leaves.

Currently building
Area Repositories
AI infrastructure guarded-db-mcp, a read-only MCP server for Oracle and PostgreSQL with PII masking and audit · rag-tr · tr-rag-eval · oracle23ai-rag
Distributed systems offline-pos-sync · webhook-relay · idempotent-api · order-saga-temporal · cdc-pipeline · outbox-lab
Healthcare & privacy patient-feedback-workflow · hbys-fhir-bridge · sut-rules · kvkk-dsar · field-crypto · merkle-audit
Databases ora2pg-verify · saas-rls-starter · plan-guard
Finance fx-bitemporal · bank-statement-recon · trkarekod · ubltr-validator
Reliability slo-chaos-lab · flags-rollout · signalr-scale-lab
Toolbox
Languages C# · SQL · PL/SQL · Python · TypeScript
Backend .NET 10, ASP.NET Core, EF Core, Dapper, SignalR, Hangfire, OpenTelemetry
Data PostgreSQL · Oracle 23ai · Redis · PostGIS · SQL Server: modelling, query tuning, CDC
Quality xUnit v3 · Testcontainers · FsCheck · NBomber · BenchmarkDotNet · Playwright
Platform Docker · GitHub Actions · OCI
Certified OCI Architect Associate · OCI Foundations Associate · Oracle AI Database Foundations

All repositories use synthetic data only. No employer or customer code, schemas or data appear on this profile.

Popular repositories Loading

  1. medula-precheck medula-precheck Public

    MEDULA invoice pre-check engine: effective-dated, illustrative SUT rules in .NET and set-based PL/SQL, with parity tests. Synthetic data only.

    C#

  2. ledger-recon ledger-recon Public

    Double-entry ledger with exactly-once posting and end-of-day card/EFT/correspondent reconciliation on PostgreSQL and .NET 10

    C#

  3. kvkk-data-inventory kvkk-data-inventory Public

    KVKK data inventory and masking tool: finds and classifies personal data in Oracle and PostgreSQL, masks it with checksum-preserving pseudonyms, generates synthetic test data and exports a VERBIS-s…

    C#

  4. hekimcan206 hekimcan206 Public

    Profile README

  5. patient-feedback-workflow patient-feedback-workflow Public

    Hospital patient-feedback workflow: HMAC-signed visit events, Oracle outbox dispatch over WhatsApp/SMS, one-time survey links, NPS/CSAT/CES, SLA cases on a live SignalR panel, encrypted PII and KVK…

    C#

  6. raf raf Public

    Grocery price comparison: Expo app + ASP.NET Core API with stale-price handling, Hangfire feed ingestion, Redis cache and SignalR live updates

    C#