Freelance delivery
Build or modernize payment rails and APIs — discovery to handoff, with milestones and docs.
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About
Four-plus years owning banking, fintech, and enterprise backends — West Africa delivery, remote worldwide.
- 4+ years in production
- Bank of Africa Group delivery via Synapse
- West Africa · Remote worldwide
- Bilingual FR / EN
Saïfoulaye Diallo
I design and own backend platforms for banking, payments, and enterprise products — services that stay correct under audit and in production.
Four-plus years in Java, Spring Boot, and distributed systems — shipping APIs, payment rails, and event-driven backends that teams can run in production.
Recent work: Synapse → Bank of Africa Group (11+ subsidiaries), FinTech rails (Wave, Orange Money, Kafka), and multi-tenant SaaS.
Based in Dakar. West Africa delivery; remote freelance and contract worldwide. Bilingual FR/EN.
Senior Backend Engineer
Dakar · West Africa · Remote Worldwide
4+
Production Years
11+
Banking subsidiaries
∞
Curiosity Driven
Languages
French
Native / full professional
English
Professional working (written)
Ways I can help
Contract embed
Backend capacity in your squad — sprints, CI/CD, and production ownership.
Architecture review
Discovery, ADRs, and reference designs before you commit budget.
Core capabilities
Where production fintech systems are won — six areas of depth from ledger design to mobile money at scale.
Payment Platforms
Design payment rails that hold up under audit and scale: idempotent by default, reconciled automatically against provider statements, and routed across payment providers without locking the business into one of them.
Stack
Java (8/11/17/21)Spring BootPostgreSQLRedisApache Kafka
Patterns: Double-entry & subledgering · Clearing & settlement automation · Cross-provider orchestration
Enterprise Backend Engineering
Build backends designed to change without rewrites — clean architecture, decoupled modules, and business logic that stays auditable as the system and the team grow. The same approach applied across 11+ Bank of Africa subsidiary integrations.
Stack
Java (8/11/17/21)Spring BootPostgreSQLApache KafkaSpring Security
Patterns: Domain-Driven Design (DDD) · Bounded context orchestration · ACID & eventual consistency
API Architecture & Governance
Design APIs as a governed product surface: contract-first, versioned, and observable — built for partner integrations that need to evolve without breaking existing consumers.
Stack
OpenAPI/SwaggerSpring Cloud GatewayJWTWebhooksHMAC
Patterns: Backward & forward-compatible APIs · Contract-first design · Configurable rate limiting
Distributed Systems Engineering
Build event-driven systems that stay correct under retries, partial failures, and regional outages — sagas, outbox, and circuit breaking applied to real payment and settlement flows, not textbook diagrams.
Stack
Apache KafkaDockerKubernetesAWS
Patterns: Saga orchestration patterns · Transactional outbox · Advanced circuit breaking
Cloud & DevOps for Regulated Delivery
Ship regulated fintech workloads with infrastructure as code, blue/green or canary rollouts, and monitoring that catches problems before customers do — audited, not just automated.
Stack
AWSKubernetesDockerTerraformGitLab CI/CD
Patterns: SLO/SLI-centric operations · Full GitOps automation · Blue/green & canary deployments
Unified Mobile Money Integrations
One API abstraction over Orange Money, Wave, MTN, and local wallets — standardized error handling, guaranteed reconciliation, and a stable contract when a new corridor launches.
Stack
Java (8/11/17/21)Spring BootPostgreSQLRedisApache Kafka
Patterns: Provider-pluggable adapters · Webhook normalization & reliability · Automated audit trails
Production stack
Tools used on live banking and fintech backends — chosen for reliability, operability, and clean handoff to your team.
Backend
Java (8/11/17/21)Spring BootSpring SecuritySpring CloudSpring BatchSpring DataSpring Integration
Data & Cache
OraclePostgreSQLRedisMySQLMongoDBCassandraElasticsearch
Messaging & APIs
RabbitMQApache KafkaOpenAPIREST APIsGraphQLgRPCWebhooksSpring Cloud Gateway
Cloud & Delivery
JenkinsGitDockerKubernetesAWSGCPGitLab CI/CDOpenTelemetryPrometheusGrafanaELK StackSplunkDatadogSentry
Frontend
AngularReactNext.jsTypeScriptTailwind CSSJavaScript (ESNext)React RouterReact Query
Fintech & Payments
Payment gateways & digital walletsMobile money platformsAutomated reconciliationISO 20022 & SWIFT messagingPayment service provider (PSP) ecosystemsDomain-driven design (DDD)Modular, clean architectureEvent-driven & CQRS patternsOutbox, Saga, and orchestration patterns
Engineering Principles
Unyielding standards for financial systems — every build engineered for trust, scale, and longevity.
Scalability
Systems architected for growth: horizontal scaling, resilient async workflows, and extensible data models that enable expansion without rewrites.
Reliability
Failure-tolerant by design — from idempotent operations and automated retries to robust fallbacks. Because real-world networks are unpredictable, but your uptime can’t be.
Security
Zero-trust methodology, signed interactions, strict least-privilege, and immutable audit logs embedded in every flow. Security is woven in, never layered on.
Maintainability
Modular by default: precise boundaries, clear contracts, and self-documenting APIs, for codebases your team can iterate on with confidence.
Performance
User-centric profiling, nuanced caching strategies, and explicit latency SLAs — performance as a feature, measured where it matters most.
Clean Architecture
Business logic at the core. Infrastructure details isolated at the edge — so your platform adapts to change, not the other way around.
Observability
Deep instrumentation, actionable telemetry, and proactive alerting empower rapid diagnosis and continuous improvement.
Ready to scope a package — or hire this profile?
Share team, stack, and constraints. I reply with a clear path: package proposal, contract embed, or next hiring steps.