Case studies

Live products and production patterns for product and platform teams. Confidential banking and FinTech work stays at pattern level.

4+ years in production
Bank of Africa Group delivery via Synapse
West Africa · Remote worldwide
Bilingual FR / EN

Architecture sprint CV Ways to work LinkedIn Contact

Ecom 360 PME

Senegal · West AfricaLive

ReactSpring BootPostgreSQLWave+2

10+

Merchants live

Hours/wk

Saved on closing

Live

West Africa

Problem

African retailers ran day-to-day operations on notebooks, spreadsheets, and improvised tills — cash errors, blind stock, forgotten customer credits, and end-of-day totals rebuilt by hand.

Solution

Commerce platform with POS, real-time inventory, Wave & Orange Money on each sale, multi-store ops, and accountant-ready exports.

Architecture

React SPA for POS and dashboards; Spring Boot multi-tenant REST API; async jobs for reports, bulk imports, and accounting exports; store-scoped inventory and role-based staff access.

Architecture, security & delivery details

Security

TLS in transit, encrypted sensitive data, automatic backups, tenant isolation per merchant, and role-based permissions for cashiers vs managers.

Scale

Multi-store chains with consolidated reporting; mobile-first UX for counter, warehouse, and field; stock decremented on every sale without manual recounts.

Architecture flow

01POS
02REST API
03Inventory
04Mobile Money
05Reporting

Constraints

Reliable counter operations, even with unstable network conditions.
Strict multi-tenant isolation by merchant and store.
Traceability for sales, customer credit, and mobile money payments.
Accountant-ready exports for local reconciliation — not raw dumps.

Decisions

Multi-tenant model

Centralize the platform while isolating operations, roles, and inventory per merchant.

Async jobs

Move exports, imports, and reports out of the checkout path to keep sales fast at the till.

Trade-offs

Operational robustness first — reliable checkout, tenant isolation, and reconciliable exports — over advanced analytics in v1.

Signal

Financial flows, local reconciliation, and multi-site ops with a minimum audit trail — patterns that transfer to FinTech delivery.

Impact

10+ merchants live across Senegal and West Africa; hours saved weekly on closing; Wave & Orange Money on every sale with accountant-ready exports.

ReactSpring BootPostgreSQLWaveOrange MoneyREST APIs

Read case study View live product

Payment Platform Disaster Lab

XOF · Dual PSP · DistributedLab · P0–P2 shipped

Java 21Spring BootKafkaPostgreSQL+3

Double capture on timeout

D1–D10

Disaster scenarios

P0–P2

Shipped today

Problem

Happy-path payment APIs are easy. The hard cases start when a PSP times out (captured or not?), the client retries after an HTTP timeout, a webhook arrives three times, a Kafka consumer dies while events pile up, or a deploy breaks 20% of traffic — perceived availability and financial correctness diverge.

Solution

Production / resilience engineering lab around a distributed payment platform: multi-service Spring Boot, dual PSP simulators, transactional outbox, and an SRE control center — proving no payment lost and none processed twice under partial failure.

Architecture

API Gateway (JWT + correlation) → payment-service (state machine, idempotency, outbox) → dual PSP simulators with Resilience4j; Postgres per service, Kafka + Schema Registry; React control center to inject chaos and observe recovery.

Architecture, security & delivery details

Security

Keycloak identity outside the business path; JWT at the gateway; X-Correlation-Id end-to-end; chaos admin endpoints scoped to PSP simulators.

Scale

Isolated failure domains — kill a consumer or PSP A/B without collapsing financial invariants; outbox lag and circuit breakers as first-class signals.

Architecture flow

01Gateway
02Payment SM
03Dual PSP
04Outbox / Kafka
05Reconciliation

Constraints

Timeout PSP ≠ FAILED — uncertainty is IN_RECONCILIATION, not a reason to call PSP B.
Failover A→B only on certain failure (503 / CB OPEN / business refuse).
Never emit a Kafka event without committed payment state (transactional outbox).
Database-per-service so the append-only ledger schema stays isolated.
PSP simulators with hot-injectable chaos — not real Stripe network/SCA behavior.

Decisions

Timeout = UNKNOWN

No blind failover on timeout; reconcile before truth — prevents double capture.

Transactional outbox

Payment commit and outbox write in one transaction so Kafka never lies about state.

Trade-offs

Correctness before “API always 200” — more payments in IN_RECONCILIATION and mandatory recon, in exchange for zero double capture on timeout.

Signal

Direct signal for payment platforms: distinguish certain PSP failure from uncertainty; idempotency, state machine, and reconciliation as first-class — not ops afterthoughts.

Impact

P0–P2 delivered: Compose stack, payment-service with idempotency and outbox, dual PSP + safe failover vs IN_RECONCILIATION, SRE control center. Disaster scenarios D1–D10 documented.

Java 21Spring BootKafkaPostgreSQLKeycloakReactResilience4j

Read case study View on GitHub

Double-Entry Ledger Platform

Fintech · Payments · WalletsReference · Modular monolith

Java 21Spring Boot 3.4PostgreSQLRedis+3

Append-only

Journal

Idempotent

Postings

Outbox

→ Kafka

Problem

Wallet and payment products need auditable money movement — balanced journals, safe retries, provider webhooks, and ops controls. A balances table plus ad-hoc updates fails compliance, idempotency, and reconciliation under load.

Solution

Production-minded modular monolith for wallets and double-entry flows: balanced journal_entries, idempotent posting, transactional outbox to Kafka, maker/checker withdrawals, and operational freeze — with a live demo UI on the real API.

Architecture

Maven modules (domain, persistence, core, platform) on Java 21 / Spring Boot 3.4; PostgreSQL + Flyway (append-only triggers); Redis rate limits; Kafka via outbox dispatcher; OpenAPI; Micrometer / optional OTLP.

Architecture, security & delivery details

Security

JWT auth, webhook HMAC verification, RBAC (ADMIN / OPERATIONS / COMPLIANCE), Redis rate limiting, and DB triggers that block UPDATE/DELETE on journal_entries.

Scale

Pessimistic account locking in deterministic order, scoped advisory locks for idempotency, scheduled reconciliation and balance snapshots — modular monolith boundaries ready to extract later.

Architecture flow

01HTTP / Webhooks
02Payment services
03Ledger posting
04Outbox / Kafka
05Reconciliation

Constraints

Every movement is a balanced journal — DB triggers enforce append-only behavior.
Retries and duplicate provider refs must dedupe via idempotency keys inside the posting transaction.
Large withdrawals may require maker/checker approval before funds leave.
Demo faucet stays sandboxed — DEMO_MODE_ENABLED must be off outside local Compose.

Decisions

Modular monolith

Split domain, persistence, application services, and HTTP adapter across Maven modules — clear boundaries without premature microservices.

Transactional outbox

Write outbox_messages in the same transaction as the post, then publish to Kafka via OutboxDispatcher.

Trade-offs

A modular monolith is easier to operate than split services, but module discipline must hold or the boundary erodes. Append-only + locking buys correctness at the cost of stricter concurrency rules on hot accounts.

Signal

Direct signal for fintech and payments teams: double-entry correctness, idempotent commands, webhook settlement, maker/checker, freeze controls, and observability — not a balances spreadsheet.

Impact

Runnable Compose stack with seeded roles, live demo UI (transfer, merchant pay, withdraw, journal expand, trial balance, approvals), Swagger, Prometheus, and Grafana — reference platform for wallet and ledger delivery.

Java 21Spring Boot 3.4PostgreSQLRedisKafkaFlywayOpenAPI

Read case study View on GitHub

Pan-African Payment SDK

West Africa corridorsProduction patterns · ENG · confidential

Confidential framing: Client code and live endpoints stay confidential. Below: reusable patterns from ENG FinTech delivery (Wave, Orange Money, Free Money) — not a public SDK dump.

JavaSpring BootRedisKafka+1

Wallets unified

API contract

Problem

Products needed separate integrations for Orange Money, Wave, and Free Money — slow launches and inconsistent error handling across providers.

Solution

One API for initiate, confirm, and reconcile — provider adapters behind a stable contract.

Architecture

Adapter pattern with Spring Boot services, Redis idempotency keys, and Kafka events for async settlement notifications.

Architecture, security & delivery details

Security

Signed requests, webhook HMAC validation, and per-tenant API keys with scoped permissions.

Scale

Horizontally scaled stateless API; provider latency isolated via async queues without blocking client threads.

Architecture flow

01Client API
02SDK
03Adapters
04Wallet Providers
05Kafka

Constraints

Heterogeneous provider APIs with inconsistent statuses and callbacks.
Retries must not create duplicate debits or duplicate notifications.
Shared observability across multiple payment corridors.
Provider credentials and live traffic remain client-confidential.

Decisions

Unified contract

Expose a stable API while hiding Wave, Orange Money, and Free Money differences behind adapters.

Explicit idempotency

Treat every payment command with a stable business key to make retries safe.

Async settlement path

Keep provider latency off the client thread with queues and Kafka settlement events so checkout stays responsive.

HMAC webhooks

Verify provider callbacks with signatures and replay windows before mutating payment state.

Trade-offs

The adapter layer adds code, but it sharply reduces integration cost and provider-specific behavior drift.

Signal

Direct signal for banks and fintechs: unified Wave, Orange Money, and wallet integrations — patterns proven on ENG Technologie FinTech delivery and applicable to multi-provider banking corridors.

Impact

Wave, Orange Money, and Free Money behind one contract — adapters, Redis idempotency, and Kafka settlement events proven on ENG FinTech delivery. Packaged SDK surface stays internal.

JavaSpring BootRedisKafkaPostgreSQL

Unified API Gateway

Multi-country bankingProduction patterns · Synapse · confidential

Confidential framing: Banking client systems stay confidential. Below: reusable gateway and API-governance patterns from Synapse delivery for Bank of Africa Group subsidiaries — not proprietary core banking code.

Spring CloudKafkaPostgreSQLDocker+1

Gateway

As boundary

Versioned

Partner APIs

Problem

A multi-entity banking group and its partners needed one entry point to payment providers and internal services — without exposing fragile core systems. Patterns drawn from Synapse consultant delivery for Bank of Africa Group subsidiaries.

Solution

Gateway for auth, routing, rate limits, and provider orchestration behind versioned REST APIs.

Architecture

Spring Cloud Gateway + domain microservices; Kafka for domain events; Jasper/reporting decoupled from transactional path.

Architecture, security & delivery details

Security

JWT at edge, RBAC, input validation before core contact, full request audit logging.

Scale

Stateless gateway tier; Kafka absorbs analytics peaks without blocking payments.

Architecture flow

01Partners
02API Gateway
03Domain Services
04Core Banking
05Audit

Constraints

Protect core systems while opening partner APIs.
Version contracts without breaking existing integrations.
Trace every sensitive request for support, audit, and compliance.
Multi-subsidiary tenancy without leaking entity boundaries.

Decisions

Gateway as boundary

Centralize authentication, rate limits, validation, and routing before any internal system contact.

Decoupled events

Publish business events outside the transactional path for reporting and observability.

Versioned partner contracts

Publish OpenAPI versions and error rules before partner exposure so multi-entity onboarding does not break existing clients.

Reporting off the hot path

Decouple Jasper/analytics via Kafka so payment and partner calls are not blocked by report generation.

Trade-offs

The gateway becomes a critical governance point; it needs discipline around versioning, monitoring, and access policies.

Signal

Aligned with multi-subsidiary banking delivery: API governance, core protection, flow auditability, and faster partner onboarding across group entities.

Impact

Patterns from Synapse delivery for 11+ Bank of Africa Group subsidiaries: gateway as the boundary, versioned partner contracts, JWT/RBAC at the edge, core systems kept off the public internet.

Spring CloudKafkaPostgreSQLDockerAWS

Want this depth on your system?

The usual first step is an architecture sprint — 1–2 weeks, €2.5k–€4.5k — then a written proposal.

Start with the sprint Ways to work

Platform Architecture

The shape of the systems in the cases — gateway, payments, events, and a store of record.

Partners & products

Who calls the backend

Partner APIsPOS & product UIProvider webhooksAdmin tools

API Gateway

Boundary before any core system

JWT & RBACRate limitingVersioned contractsTenant routing

Domain services

What the cases actually own

Payment workflowsWallet adaptersLedger & reconciliationReporting off the hot path

Events

Async path that cannot double-apply

Apache KafkaTransactional outboxAudit eventsIdempotent consumers

Data

Store of record and cache

PostgreSQLMySQLRedisAppend-only journal

Core Technologies

Java 17+Spring Boot & Spring CloudApache KafkaPostgreSQLRedisDockerKubernetesAmazon Web Services (AWS)Spring SecurityGitLab CI/CDOpenAPI & Swagger

Architectural Principles

Idempotency first — every operation is safe to retry and free of unintended side effects.
Domain events — an outbox and an immutable trail so money movement and partner calls stay explainable.
Contextual consistency — choose between eventual or strong consistency where it matters most.
Defense in depth — enforce security at every layer rather than relying on a single boundary.
End-to-end observability — continuous monitoring and traceability across services for rapid diagnosis and insight.

Technical leadership

How I lead high-stakes systems

Beyond code: framing, decisions, API governance, and delivery rituals that reduce risk in regulated environments — applied on consultant engagements such as Synapse delivery for the Bank of Africa Group.

Project leadership

Requirement analysis

Clarify business goals, regulatory constraints, core banking dependencies, and acceptance criteria before estimation.

API governance

Define OpenAPI contracts, versioning, error rules, idempotency, and access policies before partner exposure.

Risk assessment

Identify transactional risks: duplicate debit, lost callback, reconciliation drift, audit debt, or provider downtime.

Delivery control

Break work into verifiable increments with architecture reviews, code reviews, CI/CD, observability, and operable handoff.

Architecture playbook

Idempotency

Treat retries as a normal case, not a network exception.

Auditability

Trace every sensitive command with correlation ID, actor, before/after state, and source of truth.

Money movement

Separate initiation, confirmation, settlement, refunds, and reconciliation.

Reconciliation

Automate controls between internal events, the ledger, and provider statements.

Security

Apply least privilege, webhook signatures, strict validation, and audit logs.

Observability

Make ambiguous states visible with metrics, traces, alerts, and runbooks.

ADR & governance

Traceable decisions

Every structural choice should be backed by a short ADR: context, decision, consequences, and revisit condition. That lets a banking team understand why a system exists in its current shape, even six months later.

Want this depth on your system?

The usual first step is an architecture sprint — 1–2 weeks, €2.5k–€4.5k — then a written proposal.

Start with the sprint Book a call Ways to work CV

← Back to home

Case studies

Live products and production patterns for product and platform teams. Confidential banking and FinTech work stays at pattern level.

4+ years in production
Bank of Africa Group delivery via Synapse
West Africa · Remote worldwide
Bilingual FR / EN

Architecture sprint CV Ways to work LinkedIn Contact

Ecom 360 PME

Senegal · West AfricaLive

ReactSpring BootPostgreSQLWave+2

10+

Merchants live

Hours/wk

Saved on closing

Live

West Africa

Problem

African retailers ran day-to-day operations on notebooks, spreadsheets, and improvised tills — cash errors, blind stock, forgotten customer credits, and end-of-day totals rebuilt by hand.

Solution

Commerce platform with POS, real-time inventory, Wave & Orange Money on each sale, multi-store ops, and accountant-ready exports.

Architecture

React SPA for POS and dashboards; Spring Boot multi-tenant REST API; async jobs for reports, bulk imports, and accounting exports; store-scoped inventory and role-based staff access.

Architecture, security & delivery details

Security

TLS in transit, encrypted sensitive data, automatic backups, tenant isolation per merchant, and role-based permissions for cashiers vs managers.

Scale

Multi-store chains with consolidated reporting; mobile-first UX for counter, warehouse, and field; stock decremented on every sale without manual recounts.

Architecture flow

01POS
02REST API
03Inventory
04Mobile Money
05Reporting

Constraints

Reliable counter operations, even with unstable network conditions.
Strict multi-tenant isolation by merchant and store.
Traceability for sales, customer credit, and mobile money payments.
Accountant-ready exports for local reconciliation — not raw dumps.

Decisions

Multi-tenant model

Centralize the platform while isolating operations, roles, and inventory per merchant.

Async jobs

Move exports, imports, and reports out of the checkout path to keep sales fast at the till.

Trade-offs

Operational robustness first — reliable checkout, tenant isolation, and reconciliable exports — over advanced analytics in v1.

Signal

Financial flows, local reconciliation, and multi-site ops with a minimum audit trail — patterns that transfer to FinTech delivery.

Impact

10+ merchants live across Senegal and West Africa; hours saved weekly on closing; Wave & Orange Money on every sale with accountant-ready exports.

ReactSpring BootPostgreSQLWaveOrange MoneyREST APIs

Read case study View live product

Payment Platform Disaster Lab

XOF · Dual PSP · DistributedLab · P0–P2 shipped

Java 21Spring BootKafkaPostgreSQL+3

Double capture on timeout

D1–D10

Disaster scenarios

P0–P2

Shipped today

Problem

Solution

Architecture

Architecture, security & delivery details

Security

Keycloak identity outside the business path; JWT at the gateway; X-Correlation-Id end-to-end; chaos admin endpoints scoped to PSP simulators.

Scale

Isolated failure domains — kill a consumer or PSP A/B without collapsing financial invariants; outbox lag and circuit breakers as first-class signals.

Architecture flow

01Gateway
02Payment SM
03Dual PSP
04Outbox / Kafka
05Reconciliation

Constraints

Timeout PSP ≠ FAILED — uncertainty is IN_RECONCILIATION, not a reason to call PSP B.
Failover A→B only on certain failure (503 / CB OPEN / business refuse).
Never emit a Kafka event without committed payment state (transactional outbox).
Database-per-service so the append-only ledger schema stays isolated.
PSP simulators with hot-injectable chaos — not real Stripe network/SCA behavior.

Decisions

Timeout = UNKNOWN

No blind failover on timeout; reconcile before truth — prevents double capture.

Transactional outbox

Payment commit and outbox write in one transaction so Kafka never lies about state.

Trade-offs

Correctness before “API always 200” — more payments in IN_RECONCILIATION and mandatory recon, in exchange for zero double capture on timeout.

Signal

Direct signal for payment platforms: distinguish certain PSP failure from uncertainty; idempotency, state machine, and reconciliation as first-class — not ops afterthoughts.

Impact

P0–P2 delivered: Compose stack, payment-service with idempotency and outbox, dual PSP + safe failover vs IN_RECONCILIATION, SRE control center. Disaster scenarios D1–D10 documented.

Java 21Spring BootKafkaPostgreSQLKeycloakReactResilience4j

Read case study View on GitHub

Double-Entry Ledger Platform

Fintech · Payments · WalletsReference · Modular monolith

Java 21Spring Boot 3.4PostgreSQLRedis+3

Append-only

Journal

Idempotent

Postings

Outbox

→ Kafka

Problem

Solution

Architecture

Architecture, security & delivery details

Security

JWT auth, webhook HMAC verification, RBAC (ADMIN / OPERATIONS / COMPLIANCE), Redis rate limiting, and DB triggers that block UPDATE/DELETE on journal_entries.

Scale

Pessimistic account locking in deterministic order, scoped advisory locks for idempotency, scheduled reconciliation and balance snapshots — modular monolith boundaries ready to extract later.

Architecture flow

01HTTP / Webhooks
02Payment services
03Ledger posting
04Outbox / Kafka
05Reconciliation

Constraints

Every movement is a balanced journal — DB triggers enforce append-only behavior.
Retries and duplicate provider refs must dedupe via idempotency keys inside the posting transaction.
Large withdrawals may require maker/checker approval before funds leave.
Demo faucet stays sandboxed — DEMO_MODE_ENABLED must be off outside local Compose.

Decisions

Modular monolith

Split domain, persistence, application services, and HTTP adapter across Maven modules — clear boundaries without premature microservices.

Transactional outbox

Write outbox_messages in the same transaction as the post, then publish to Kafka via OutboxDispatcher.

Trade-offs

Signal

Direct signal for fintech and payments teams: double-entry correctness, idempotent commands, webhook settlement, maker/checker, freeze controls, and observability — not a balances spreadsheet.

Impact

Java 21Spring Boot 3.4PostgreSQLRedisKafkaFlywayOpenAPI

Read case study View on GitHub

Pan-African Payment SDK

West Africa corridorsProduction patterns · ENG · confidential

Confidential framing: Client code and live endpoints stay confidential. Below: reusable patterns from ENG FinTech delivery (Wave, Orange Money, Free Money) — not a public SDK dump.

JavaSpring BootRedisKafka+1

Wallets unified

API contract

Problem

Products needed separate integrations for Orange Money, Wave, and Free Money — slow launches and inconsistent error handling across providers.

Solution

One API for initiate, confirm, and reconcile — provider adapters behind a stable contract.

Architecture

Adapter pattern with Spring Boot services, Redis idempotency keys, and Kafka events for async settlement notifications.

Architecture, security & delivery details

Security

Signed requests, webhook HMAC validation, and per-tenant API keys with scoped permissions.

Scale

Horizontally scaled stateless API; provider latency isolated via async queues without blocking client threads.

Architecture flow

01Client API
02SDK
03Adapters
04Wallet Providers
05Kafka

Constraints

Heterogeneous provider APIs with inconsistent statuses and callbacks.
Retries must not create duplicate debits or duplicate notifications.
Shared observability across multiple payment corridors.
Provider credentials and live traffic remain client-confidential.

Decisions

Unified contract

Expose a stable API while hiding Wave, Orange Money, and Free Money differences behind adapters.

Explicit idempotency

Treat every payment command with a stable business key to make retries safe.

Async settlement path

Keep provider latency off the client thread with queues and Kafka settlement events so checkout stays responsive.

HMAC webhooks

Verify provider callbacks with signatures and replay windows before mutating payment state.

Trade-offs

The adapter layer adds code, but it sharply reduces integration cost and provider-specific behavior drift.

Signal

Direct signal for banks and fintechs: unified Wave, Orange Money, and wallet integrations — patterns proven on ENG Technologie FinTech delivery and applicable to multi-provider banking corridors.

Impact

Wave, Orange Money, and Free Money behind one contract — adapters, Redis idempotency, and Kafka settlement events proven on ENG FinTech delivery. Packaged SDK surface stays internal.

JavaSpring BootRedisKafkaPostgreSQL

Unified API Gateway

Multi-country bankingProduction patterns · Synapse · confidential

Spring CloudKafkaPostgreSQLDocker+1

Gateway

As boundary

Versioned

Partner APIs

Problem

Solution

Gateway for auth, routing, rate limits, and provider orchestration behind versioned REST APIs.

Architecture

Spring Cloud Gateway + domain microservices; Kafka for domain events; Jasper/reporting decoupled from transactional path.

Architecture, security & delivery details

Security

JWT at edge, RBAC, input validation before core contact, full request audit logging.

Scale

Stateless gateway tier; Kafka absorbs analytics peaks without blocking payments.

Architecture flow

01Partners
02API Gateway
03Domain Services
04Core Banking
05Audit

Constraints

Protect core systems while opening partner APIs.
Version contracts without breaking existing integrations.
Trace every sensitive request for support, audit, and compliance.
Multi-subsidiary tenancy without leaking entity boundaries.

Decisions

Gateway as boundary

Centralize authentication, rate limits, validation, and routing before any internal system contact.

Decoupled events

Publish business events outside the transactional path for reporting and observability.

Versioned partner contracts

Publish OpenAPI versions and error rules before partner exposure so multi-entity onboarding does not break existing clients.

Reporting off the hot path

Decouple Jasper/analytics via Kafka so payment and partner calls are not blocked by report generation.

Trade-offs

The gateway becomes a critical governance point; it needs discipline around versioning, monitoring, and access policies.

Signal

Aligned with multi-subsidiary banking delivery: API governance, core protection, flow auditability, and faster partner onboarding across group entities.

Impact

Patterns from Synapse delivery for 11+ Bank of Africa Group subsidiaries: gateway as the boundary, versioned partner contracts, JWT/RBAC at the edge, core systems kept off the public internet.

Spring CloudKafkaPostgreSQLDockerAWS

Want this depth on your system?

The usual first step is an architecture sprint — 1–2 weeks, €2.5k–€4.5k — then a written proposal.

Start with the sprint Ways to work

Platform Architecture

The shape of the systems in the cases — gateway, payments, events, and a store of record.

Partners & products

Who calls the backend

Partner APIsPOS & product UIProvider webhooksAdmin tools

API Gateway

Boundary before any core system

JWT & RBACRate limitingVersioned contractsTenant routing

Domain services

What the cases actually own

Payment workflowsWallet adaptersLedger & reconciliationReporting off the hot path

Events

Async path that cannot double-apply

Apache KafkaTransactional outboxAudit eventsIdempotent consumers

Data

Store of record and cache

PostgreSQLMySQLRedisAppend-only journal

Core Technologies

Java 17+Spring Boot & Spring CloudApache KafkaPostgreSQLRedisDockerKubernetesAmazon Web Services (AWS)Spring SecurityGitLab CI/CDOpenAPI & Swagger

Architectural Principles

Idempotency first — every operation is safe to retry and free of unintended side effects.
Domain events — an outbox and an immutable trail so money movement and partner calls stay explainable.
Contextual consistency — choose between eventual or strong consistency where it matters most.
Defense in depth — enforce security at every layer rather than relying on a single boundary.
End-to-end observability — continuous monitoring and traceability across services for rapid diagnosis and insight.

Technical leadership

How I lead high-stakes systems

Project leadership

Requirement analysis

Clarify business goals, regulatory constraints, core banking dependencies, and acceptance criteria before estimation.

API governance

Define OpenAPI contracts, versioning, error rules, idempotency, and access policies before partner exposure.

Risk assessment

Identify transactional risks: duplicate debit, lost callback, reconciliation drift, audit debt, or provider downtime.

Delivery control

Break work into verifiable increments with architecture reviews, code reviews, CI/CD, observability, and operable handoff.

Architecture playbook

Idempotency

Treat retries as a normal case, not a network exception.

Auditability

Trace every sensitive command with correlation ID, actor, before/after state, and source of truth.

Money movement

Separate initiation, confirmation, settlement, refunds, and reconciliation.

Reconciliation

Automate controls between internal events, the ledger, and provider statements.

Security

Apply least privilege, webhook signatures, strict validation, and audit logs.

Observability

Make ambiguous states visible with metrics, traces, alerts, and runbooks.

ADR & governance

Traceable decisions

Want this depth on your system?

The usual first step is an architecture sprint — 1–2 weeks, €2.5k–€4.5k — then a written proposal.

Start with the sprint Book a call Ways to work CV