Mustafa Özpinar

I worked on the design and development of a document generation and distribution service driven by Kafka events and REST APIs. The service aggregated data from multiple microservices, rendered documents using Aspose, and stored them in Amazon S3. Outputs were delivered via email and SFTP, with partner notifications sent through webhooks and feature-based behavior controlled using Split feature flags.

The platform supported multi-tenant integrations secured with Okta and JWT, enabling continuous onboarding of new partners. To improve scalability, I contributed to a new version of the services built with CQRS, event modeling, and additional microservices.

I also designed an email ingestion pipeline using SES, SNS, and SQS, parsing EML files and integrating them into the system with event sourcing and CQRS. In addition, I worked on a centralized notification system that consumed Kafka events, filtered and mapped messages, and delivered notifications via Svix or direct webhooks, later refactored to a listener-based architecture for better flexibility and operability.

Developed a high-throughput microservice with Java, Spring Boot, Kafka, and Akka (Alpakka). A single instance of the microservice can transform 5 KB of data per second, run load tests, and analyze them with New Relic dashboards. Tuning Akka, resources, and Kafka parameters resulted in processing 3x faster. I created integration tests using Testcontainers and deployed Docker images built via GitHub Actions to GKE with Harness.

Architected and developed SAML and OIDC-based IdP solutions for face recognition APIs. I developed plugins for Keycloak and designed the flow for web, mobile, and external IdP integrations. I also created client applications for Android, Node.js, and Java.

Users have wallets in eCommerce platforms. Deposit, pay, withdraw, refund, and rebates are features of the wallet service.
• Event sourcing with Axon framework
• CQRS pattern (PostgreSQL for events and commands and Couchbase for reading)
• Live system with high traffic

A Kafka library used in many microservice application projects. I was on the team of architects that developed the library.

Configurable features:
• Inbox/outbox pattern
• Priority queue
• Message retry
• Security with KeyCloak integration
• Log enrichment
• Message header transmission over REST to Kafka and Kafka to Kafka
• Breadcrumbs for messages
• Annotation-based command and event and command result handlers
• Annotation-based error handling
• Message transmission with large payload automatically over Redis
• Message tracing enabled with follow-up

A client-server application for managing versions of a microservice-based product.

It has the following features:

• CRUD on microservice definitions.
• CRUD on projects/products/product versions.
• Projects contain products. Products consist of microservices and selected versions.
• CRUD on release management. Users can define releases, select microservices and deploy to specified Kubernetes environments.
• Users can define Kubernetes environments (SSH connections).
• Release process can be monitored live.
• Users can log in.
• UI developed with React and PrimeReact library. Redux is used for state management.
• Back end exposes REST APIs as Spring Boot applications.

An Android application developed for a customer mainly reading and listening Book. It was published to Google Playstore and updated periodically. I designed and developed the whole application from scratch.

It has the following features:

• User can read and listen to pages.
• Pages and sounds can be downloaded optionally.
• Music can be controlled from the notification bar and lock screen.
• Selected play configuration can be saved to quickly use later.
• Page translation and commentary can be read.
• Page, translation, and commentary sources can be selected.
• Search from translation.
• Indexed search
• Settings contain font, storage, downloaded file management, background, etc.
• Share selected verse(s)
• Manage cache for performance
• Downloaded files are encrypted and decrypted when used.

A prototype single soldier system project containing a smartphone, smartwatch, heart rate monitor, and smart glass. The soldier can see real-time data on their team and hostiles.

Key activities:
• Developed an Android application for smartphones with GIS capabilities.
• Built an Android application for smartwatches.
• Designed and implemented software for smart glass.
• Integrated all hardware using the Bluetooth protocol.
• Published and gathered data with the team and C4I system.

Many features in the fire support domain, such as unit, communication infrastructure, GIS, settings, tools, user management, and navigation, are common between similar projects. In this SPL project, variabilities and commonalities are managed systematically, spanning all phases of the product lifecycle, from design to test.

Sixteen different projects were produced from this SPL in five years with an average of 80% reuse. The team developed many of the tools that were required to manage the SPL.

A system that tracks a country's forces and shares data with allies. Each force can send its data to the server based on selected communication media. The collector software integrates with C4I systems using different protocols. Security was and is crucial in this project.

A patent/trademark attorney has a company that acts as a proxy for clients who apply for a patent, register a trademark, or apply for a design approval.

Features:
• CRUD on trademark, patent, design, and geographical indications
• Bulletins published by the TPI can be loaded into the system
• Detailed search and alert mechanisms are available on existing bulletins
• Client management
• Workflow management
• Alert management
• Many kinds of reports based on the JasperReports tool
• Integration with TPI's XML-based application feature
• Payment tracking

The TPI has many internal and external applications, such as trademarks, patents, designs, laws, publications, and attorneys. Experts in the institute use these applications for all workflows based on their domains integrated with document management and authentication/authorization systems. On the other side, external users can search, apply, and check the status of documents and perform some actions on the website.

An e-learning project focused mainly on the United States market. As the full-stack developer for configuration management in the admin panel, I integrated the project with a business partner's product using SSO with a SAML protocol. I also built the load balancing infrastructure using the Apache HTTP Server backed by Apache Tomcat using sticky sessions.