Public case studies · 2026 edition
Nawfal Alim Fardana
Lead software engineer - payments & distributed systems
years payment infrastructure
daily users served
Ant Group ecosystem
engineering case studies
Chapter 01 · Fintech backend engineering
Arus - Double-Entry Ledger
A production Go ledger proving money correctness through explicit locks, transactional outbox delivery, load evidence, and Family Finance shadow writes.
Editorial index
Chapters in the dossier
- 02
Backend engineering
Family Finance
A multi-surface household finance platform with web, mobile, integrations, and backend-owned API boundaries.
- Go backend and Next.js web app split across stable API contracts
- Recruiter-readable UI flow and native mobile journey evidence
- Honest backend maturity roadmap for Redis, Kafka, jobs, and observability
Published - 03
Product and platform engineering
WebhookOps Audit
A live webhook operations audit demo shaped through PRD, system analysis, QA, and implementation docs.
- Live Cloud Run demo with token-gated access
- Documented SDLC artifacts from PRD through QA
- Webhook event handling and operational workflow framing
Published - 04
Mobile and backend engineering
Strava AI Insights
A Strava companion whose owner audited his own product like an attacker, found auth and IDOR risks, then shipped source-backed hardening.
- Self-audit found a missing auth layer, a client-trusted athleteId flow, and a practical IDOR chain
- Fixes include signed mobile sessions, bearer ownership checks, token encryption, and controller security tests
- Open gates stay visible: live OAuth/device QA, revocation, migrations, and diagnostic search caveats
Published - 05
Platform engineering
Telegram Bot
A Hermes-based development bot proving agentic systems need enforcement layers, not instructions, before write-capable operations are trusted.
- Security audit blocks direct GitHub write tools, sensitive paths, secret-like content, and unsafe MCP exposure
- Action and completion audits cover proposal history, approval state, repository gates, and Cloud Build triage
- Open limits remain explicit: real approved PR flow, operator live setup, credential rotation, and Hermes model hooks
Published - 06
Payments and settlement engineering
Selaras - Settlement Reconciliation
A Java/Spring Batch reconciliation engine that closes the Arus v1 loop with seeded break proof, balanced reports, and honest fixture-demo limits.
- 5/5 break classes detected in the M3 demo transcript and seeded integration test
- 0 false matches: planted broken records stay out of match rows
- Report generation fails unless matched plus breaks balances to line counts
Published - 07
Payments orchestration engineering
Alur - Payment Orchestration
A Go payment orchestration service that survives hostile PSP behavior with a 500-intent chaos gate, reaper truth, and exactly-once Arus booking.
- 500-intent chaos storm covers timeout-after-charge, 5xx, duplicate webhooks, and out-of-order delivery
- 0 double charges after reaper convergence and leased refund retries
- Exactly-once Arus booking via same-transaction outbox and external-ref replay
Published - 08
Disputes & chargeback engineering
Banding - Dispute Lifecycle Engine
A Go dispute and chargeback lifecycle engine proving durable deadlines, deterministic network events, and exactly-once Arus writebacks.
- 500-dispute deadline storm covers every reason code and scenario token
- 0 non-terminal and 0 past-deadline awaiting disputes after convergence
- Exactly-once balanced writebacks with a restart-safe durable due_at scheduler
Published
Now building
Banding roadmap
Seed CLI, outbox max-attempts sweep, network-format fidelity, and the gated deploy are now tracked from the shipped Banding chapter.