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The problems I solve, and the proof behind them.
Each domain links a class of problem to real work. Technologies are listed in their usage context, not as badges.
01
Backend engineering
Backend services that stay readable and testable as scope grows: multi-tenancy, modularity, explicit contracts.
Typical problems
- Core services that are hard to evolve
- Multi-tenancy bolted on after the fact
- Integration debt between teams
Stack in context
Java · Spring Boot · PostgreSQL · JPA/Flyway
02
Payments & FinTech
Payment flows where every state matters: accepted, confirmed, settled. Idempotency, reconciliation, and audit trails.
Typical problems
- Duplicate payments on retries
- SUCCESS callbacks that are not settled
- Gaps between ledger and statements
Stack in context
Redis (idempotency) · Kafka (settlement) · double-entry ledger
03
API integration
Single entry points to fragile systems: authentication at the edge, versioning, stable partner contracts.
Typical problems
- Core systems exposed publicly
- Inconsistent partner integrations
- Contract breaks in production
Stack in context
API gateway · JWT/RBAC · OpenAPI
04
Distributed systems & reliability
Design for partial failure: what happens when a provider times out, a consumer replays, or a service goes down.
Typical problems
- Lost or duplicated events
- Outages without diagnosis
- Unsafe failover
Stack in context
Kafka · outbox · OpenTelemetry · Prometheus/Grafana