nikitajvm

* Eliminated live-payment 'stalls' in production by implementing a 2-queue priority system (live vs. bulk) without scaling costs and without modifying the fragile legacy core. The approach's effectiveness was proven on a PoC model, showing a p99 reduction from ~4.3 minutes to 182ms ([analysis, demo-experiment, and article based on them](https://github.com/nikita-kibitkin/two-queue-priority-demo/blob/master/article/article.md)). * Co-authored the company's core proprietary technology. Officially recognized as a key architect and IP contributor for the 'DucatPay Software'. * Restored 4.5M+ recurring payment records after an infrastructure incident involving data loss in the primary Riak DB. To do this, I proactively proposed and developed a controllable batch process (based on schedulers and DB tables) that pulled raw data from Kafka. This preserved subscription revenue and prevented legal issues. * Designed and implemented (on 8+ key microservices) a centralized configuration and secrets management system (**Spring Cloud, HashiCorp Vault**), ensuring zero-downtime application of changes. * Developed and implemented a standardized Git Flow, which allowed the DevOps team to fully automate CI/CD for all new microservices (previously required manual intervention). * Unified adapter functionality by extracting common logic and operational flow construction into core libraries, reducing new adapter development time by ~**2x**. * Hired and onboarded 2 Mid-level developers (from a funnel of ~10 interviews) who have been working successfully on the team for **over a year**. * Automated report generation and distribution (generated **8.4k+** in prod), saving **2100+ hours** of manual labor. This reduced the support team's workload and provided the business with **metrics to control financial indicators**. * Eliminated a Kafka pipeline bottleneck with 0% downtime, **preventing traffic stoppages** during recurring payment peaks. Reduced topic lag from **60,000 to <10 messages** through tuning (linger, batch, partitions). * Optimized CI/CD (GitLab CI) by implementing Docker layer caching and slim images (Alpine) with full compatibility checks (musl), significantly speeding up build times. * Was responsible for the development and support of API integrations with external payment partners, implementing 2 key adapters and achieving **~100%** coverage for client operations (disbursements & collections). * Developed analytics services (Kafka consumers) responsible for enriching, storing (DB), and exporting (**XLSX, S3**) business data on demand.

* Performed a decomposition of the payment core: extracted 4 provider integrations into separate stateless services (adapters), while maintaining the shared DB and core orchestration within the monolith. * Initiated the modernization of payment flows, successfully migrating 2 service-adapters to the Zeebe BPMN engine. * Developed 3 Kafka consumer microservices to process 'raw' data and send it asynchronously to analytics systems (Firebase, GA).

* Implemented 'Configuration as Code' for Keycloak using its Java API client to ensure consistency and eliminate manual configuration of the authorization service between dev/stage/prod environments. * Was responsible for the development and support of API integrations with external payment partners (disbursements & collections), achieving ~80% coverage for client operations.