Back End Developer

Backend Engineer (Golang) — Core Prepaid Platform

*📍 Location:* Bandung, Indonesia & Malang, East Java

*💼 Type:* Full-time

*🏢 Domain:* Digital Banking / Payment Systems

*🗓️ Experience:* Minimum 2+ years

🚀 About the Role

We're modernizing a mission-critical *Core Prepaid Platform* for one of Indonesia's largest payment ecosystems — think real-time transaction processing, card lifecycle management, settlement engines, and fraud detection at national scale. This is not a maintenance job. You'll be building the backbone of a next-generation payment host from the ground up, designed to run *in parallel with a legacy system* during a carefully orchestrated coexistence phase.

If the words "atomic balance updates under high concurrency" make your eyes light up — keep reading.

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🛠️ What You'll Build

- *Real-time transaction engine* — top-up, purchase/deduct, reversal, and correction flows with strict idempotency guarantees

- *Batch processing pipelines* — settlement files, reconciliation, journal generation with checkpoint/restart capabilities

- *Card & account lifecycle services* — state machines for issuance, activation, block/unblock, replacement, and closure

- *Integration layer* — REST APIs and file-based interfaces with enterprise middleware, journaling platforms, and security services

- *Observability-first services* — structured logging, correlation IDs, metrics, and end-to-end traceability baked in from day one

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💻 Our Stack

| Layer | Tech |

| *Language* | Go (Golang) |

| *HTTP Framework* | Chi / Fiber |

| *Data Access* | sqlc (type-safe, code-generated SQL) |

| *Database* | PostgreSQL (or similar RDBMS) |

| *Messaging/Queue* | Kafka / Redis (nice to have) |

| *Observability* | Structured logging, metrics, distributed tracing |

| *Infra* | Docker, CI/CD, Kubernetes (nice to have) |

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✅ What We're Looking For

Must-Haves:

- 2+ years of professional backend experience, with solid hands-on Go in production

- Strong understanding of concurrency patterns in Go: goroutines, channels, mutexes, and worker pools — you'll need this for a high-concurrency transaction engine where balance consistency is non-negotiable

- Familiar with idempotency patterns — duplicate detection, retry-safe APIs, request deduplication, exactly-once semantics

- Deep understanding of database transactions, isolation levels, and locking (no partial postings on your watch)

- Experience designing and documenting RESTful APIs with versioning and backward compatibility in mind

- Comfortable writing clean, testable, well-documented code — unit and integration tests are part of the definition of done

- Solid grasp of error handling, timeouts, retries, and graceful degradation in distributed systems

Nice-to-Haves (Bonus Points ✨):

- Previously involved in banking or financial systems — payments, core banking, e-money, card systems, or settlement engines

- Familiarity with financial transaction flows: payment, settlement, reconciliation, journaling, reversal/correction handling

- Experience with batch/file processing (control totals, duplicate file checks, staging & quarantine patterns)

- Understanding of maker-checker workflows, audit trails, and data masking requirements

- Exposure to PCI-DSS or similar financial security/compliance standards

- Experience with migration/coexistence scenarios — running new systems alongside legacy ones with routing-based rollout

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🎯 What Success Looks Like (First 6 Months)

- You ship transaction services where no retry ever causes a double posting

- Your services survive failure scenario testing — timeouts, dependency outages, failover — with zero lost or duplicated transactions

- Your code passes concurrency and load tests under high TPS with consistent balance outcomes

- Every transaction you process is fully traceable end-to-end via correlation references

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🌱 Why Join Us

- Real scale, real stakes — your code handles actual money movement for millions of users

- Greenfield architecture* — no legacy tech-debt hell on your side of the fence; you help define the patterns

- Engineering rigor culture — proper SIT/UAT cycles, failover drills, DR testing, and code reviews that actually matter

- Vendor-neutral mindset — we value engineers who understand why, not just how to use a framework

- Growth path — this platform is built to evolve; there's plenty of room to own bigger pieces

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📬 How to Apply

Send your CV/resume (and optionally your GitHub/portfolio) to developer@siesta.id with the subject:

> Backend Engineer (Go) — [Your Name]

*Shortlisted candidates will go through:*

1. 📋 CV screening

2. 💻 Technical assessment (Go concurrency + system design — yes, we'll ask about idempotency 😉)

3. 🗣️ Technical interview

4. 🤝 Culture fit & final interview

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We welcome applicants from all backgrounds. If you don't tick every box but believe you can handle high-concurrency financial systems — apply anyway.

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