Fajar Nurrachmat Hidayat
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Available for freelance projects

Fajar Nurrachmat Hidayat

Payment Systems Integration Engineer

Payment Systems Integration Engineer with an 8-year technical foundation across payment systems, full-stack web development, and infrastructure reliability. Specialist in SNAP ASPI implementations (VA, QRIS, Direct Debit), OAuth 2.0, signature verification, and log-level observability.

Contact me Selected work
Portrait of Fajar Nurrachmat Hidayat, Payment Systems Integration Engineer

Key facts

Location
Jakarta Utara
Experience
8+ years in IT
Current
Payment Systems Integrator, PT. Sahabat Kirim Digital
Focus
SNAP ASPI (VA, QRIS, Direct Debit), OAuth 2.0, Webhook Idempotency
Education
S1 Informatics Engineering, STIKOM Cipta Karya Informatika
Languages
Indonesian (native), English (working)

Skills

Payment and integration
SNAP ASPI (VA, QRIS, Direct Debit), OAuth 2.0 (B2B/B2B2C), REST APIs, Webhook idempotency, UAT scenario design
Security and cryptography
Asymmetric signatures (SHA256withRSA), symmetric signatures (HMAC-SHA512), public/private key lifecycle, payload hashing
Development and databases
Go, PHP (Laravel, CodeIgniter), JavaScript, jQuery, PostgreSQL, MySQL, Redis
Tools and infrastructure
Grafana, Loki (LogQL), Postman, Git, Docker, Winbox, Linux/MikroTik networking

Selected work

Two independent products running in production, and a case study from payment gateway integration work.

Bagi Sinyal landing page with a market ticker and a live signal stream
Live product

Bagi Sinyal

Quantitative trading and investing navigator for IDX stocks and crypto. It scans technical and fundamental market data in real time, delivers tactical entry signals, and screens undervalued stocks for long-term investing.

Full-stack architecture · PostgreSQL and Redis · REST API

Visit product (bagisinyal.web.id) (opens in a new tab)
Garis Waktu Photo home screen with a photo strip preview and three steps
Live product

Garis Waktu Photo

Photo strip maker in the Korean photobooth style, running in the browser. Pick a frame, shoot with the camera or upload, decorate with stickers, and download. Frames and stickers are free.

WebRTC camera access · HTML5 Canvas compositing · UI performance

Visit product (photoboxkuy.web.id) (opens in a new tab)
Integration workflow
  1. 1. Sandbox access and credentials
  2. 2. OAuth token and signature checks
  3. 3. Callback and payload validation
  4. 4. UAT sign-off with the merchant or partner
  5. 5. Production go-live and log monitoring
Status: UAT to Production
Case study

Payment gateway integration, from UAT to production

Guiding merchants and partners through integration at PT. Sahabat Kirim Digital: validating callbacks, resolving transaction bottlenecks, and tracing root causes through Grafana Loki logs.

SNAP ASPI · OAuth · Grafana Loki · Root-cause analysis

Try the callback simulator

SNAP ASPI callback simulator

Choose a scenario and trigger a callback to see how the checks play out in a Loki-style log stream. All data is simulated and uses dummy keys.

Select scenario
job="snap-callback" · simulated
200 OK
10:21:04.102 INFO callback.received POST /v1.0/transfer-va/payment from partner=demo-bank
10:21:04.180 INFO auth.oauth Bearer token valid (B2B access token, expires in 842s)
10:21:04.225 INFO signature.verify X-SIGNATURE HMAC-SHA512 matched
10:21:04.280 INFO payload.validate partnerReferenceNo unique, amount matches
10:21:04.310 OK response HTTP 200 {"responseCode":"2002500","responseMessage":"Successful"}
Inspect SNAP callback headers, raw payload & HMAC signature:

Experience

  1. 09/2025 – Present

    Merchant Integrator

    PT. Sahabat Kirim Digital · Payment systems and partner integration

    Spearheads end-to-end payment gateway onboarding under SNAP ASPI specifications: managing OAuth 2.0 token cycles, cryptographic signature validations (SHA256withRSA, HMAC-SHA512), and webhook idempotency. Diagnoses transaction drops and payload anomalies via LogQL telemetry in Grafana Loki.

  2. 01/2024 – 09/2025

    Full Stack Developer

    PT. Odisys Indonesia

    Architected and maintained scalable multi-tier web applications using PHP (Laravel/CodeIgniter), Go, and PostgreSQL/MySQL. Lowered query and API latency by refactoring endpoints, indexing database tables, and integrating Redis caching.

  3. 12/2021 – 12/2023

    IT Application Support

    PT. Odisys Indonesia

    Maintained high availability across enterprise application environments under strict SLAs, published technical Root-Cause Analysis (RCA) reports on recurring defects, and executed pre-release patch validations.

  4. 03/2017 – 03/2021

    IT Support

    PT Indomarco Prismatama

    Maintained hardware uptime and transaction continuity for distributed retail POS systems, local database instances, and branch LAN/WAN network infrastructure via MikroTik and Winbox.

Education

  1. 2019 – 2023

    S1 Informatics Engineering

    STIKOM Cipta Karya Informatika

    GPA 3.41 / 4.00

Contact

Open to freelance projects and integration work. Message me directly, or send a request over HTTP if you prefer.

Message on WhatsApp (opens in WhatsApp in a new tab) Send an email
Location: Jakarta Utara, Indonesia
Send a request over HTTP 
curl -X POST https://fnurrachmat.web.id/api/contact \
  -H "Content-Type: application/json" \
  -d '{"name":"...","email":"...","message":"..."}'

Send a message