Blockchain Engineer

BangoPure Limited is seeking a skilled Blockchain Engineer to join our international team on a full-time, remote basis. The successful candidate will focus on developing and maintaining the on-chain hash anchoring and verification layer of our platform, which supports sustainability, traceability, and digital transformation initiatives. This role requires strong expertise in Java and Spring Boot, with a specific emphasis on blockchain applications using Polygon for hash anchoring rather than token issuance or NFT minting. You will work on a production-ready modular monolith platform, contributing to backend services and ensuring robust integration with external systems.

Key Responsibilities
- Design, develop, test, and maintain the on-chain hash anchoring and verification layer using web3j, Solidity 0.8, and Polygon.
- Enhance and secure the passport mint pipeline, an event-driven saga over Apache Kafka, covering product submission, assessment, environmental declaration calculation, GS1 identifier assignment, passport generation, on-chain anchoring, and EU DPP Registry registration.
- Ensure the anchoring process is idempotent and resilient, managing compensation paths, retries, duplicate events, transaction confirmation, and failure recovery.
- Develop public verification tools enabling consumers and regulators to validate passport records against anchored hashes.
- Implement tamper-evident audit trails with hash chaining and support compliance features such as GDPR erasure flows and data export SLAs.
- Integrate with external systems including GS1 Digital Link resolvers, the EU DPP Registry, and sector-specific rule sets for batteries and electronics, strictly following published specifications.
- Deliver new hexagonal feature modules (verification, billing, supplier onboarding, developer APIs) with isolated data and events, released behind feature flags.
- Contribute to multi-tenancy features including PostgreSQL row-level security, tenant-scoped search, and tests ensuring strict tenant data isolation.
- Conduct smart contract testing and security reviews for anchoring contracts.
- Produce architecture decision records prior to implementation and maintain technical documentation aligned with specification documents.
- Collaborate closely with Product Owners, backend engineers, DevOps, QA, and business stakeholders throughout the development lifecycle.

Required Qualifications
- Minimum 3+ years of hands-on experience building backend services in Java, primarily using Spring Boot.
- Practical experience with EVM-compatible blockchains (Ethereum, Polygon, or similar), including Solidity smart contract development and backend integration.
- Strong knowledge of relational databases, including query optimization, safe migrations, and transaction management.
- Experience with asynchronous messaging systems such as Apache Kafka, RabbitMQ, or AWS SQS, including handling at-least-once delivery, duplicate events, and consumer lag.
- A disciplined testing approach, including integration tests against real infrastructure, written before considering work complete.
- Proven ability to translate detailed specifications, regulations, or API contracts into precise code, raising ambiguities rather than making assumptions.
- Proficient written English for asynchronous collaboration across multiple time zones.
- Ability to work independently within a fully remote, international team.

Preferred Qualifications and Benefits
- Experience with hexagonal (ports-and-adapters) architecture or Spring Modulith.
- Background in building multi-tenant SaaS platforms, especially using PostgreSQL row-level security.
- Familiarity with regulated domains such as GDPR, supply chain traceability, GS1 standards, or sustainability reporting.
- Knowledge of event sourcing, sagas, and transactional outbox patterns.
- Understanding of Digital Product Passport (DPP) concepts and the EU ESPR framework.
- Hands-on experience with Elasticsearch, jOOQ, or OpenTelemetry is a plus.

Technical Environment
- Java 21 with virtual threads, Spring Boot 3.4, Spring Modulith, Spring Security.
- Blockchain tools including web3j, Solidity 0.8, Polygon, and smart contract testing frameworks like Hardhat or Foundry.
- PostgreSQL with row-level security, JPA, jOOQ, Flyway migrations.
- Apache Kafka with Confluent Schema Registry (Avro) and transactional outbox pattern.
- Additional data stores: Redis, MongoDB, Elasticsearch, Amazon S3 (EU region).
- Build and testing tools: Gradle 8 (Kotlin DSL), JUnit 5, Testcontainers, contract tests for events.
- DevOps and observability: Docker, Helm, Kong API Gateway, Prometheus, Grafana, OpenTelemetry.

Additional Expectations
- Adherence to a delivery standard of one task per branch and merge request, with comprehensive testing and migration coverage.
- Commitment to treating repository specification documents as the authoritative source.
- Willingness to participate in thorough code reviews focusing on security and quality.
- Self-motivation to work through detailed written backlogs without close supervision.
- Strong documentation and technical writing skills.

What We Offer
- Fully remote position with flexible working hours.
- Opportunity to work on regulated blockchain and sustainability solutions.
- Exposure to Digital Product Passport (DPP), AI, and emerging technologies.
- Career growth opportunities within a collaborative international team environment.

Join BangoPure Limited and contribute to building secure, verifiable, and compliant blockchain solutions that advance sustainability, traceability, and digital transformation on a global scale.