Ahmet Karakaya, Developer in Istanbul, Turkey
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Ahmet Karakaya

Verified Expert  in Engineering

Software Developer

Location
Istanbul, Turkey
Toptal Member Since
July 2, 2021

Ahmet is a software engineering architect, team lead, and expert in communication technologies. He is skilled in Java, Python, Java Native Interface (JNI), Kafka, Cassandra, and Redis. Ahmet excels in finding solutions for the biggest problems in distributed systems, such as linear scalability, performance utilization, and concurrency.

Portfolio

Yaacov Silberman
Architecture, VoIP, Session Initiation Protocol (SIP), Peer-to-peer Networking...
MUFG Investor Services - Main
Java, Spring Boot, Angular, SSL, Oracle, Amazon Web Services (AWS), ActiveMQ...
PhysIQ, Inc.
Python, Kotlin, Java, Gherkin, Git, Automated Testing, Kubernetes...

Experience

Availability

Full-time

Preferred Environment

Java, Spring Boot, Apache Kafka, Redis, Git, Agile Software Development, High-load, WebRTC, Python 3

The most amazing...

...project I've guided was the development of the BiP messaging application platform with 50 million users.

Work Experience

Senior Full-stack Architect Developer

2024 - 2024
Yaacov Silberman
  • Designed the Session Initiation Protocol (SIP) platform and proposed alternative solutions.
  • Investigated and recommended SIP/WebRTC devices specific to kids.
  • Discussed business discussions collaborating with the client, an entrepreneur.
Technologies: Architecture, VoIP, Session Initiation Protocol (SIP), Peer-to-peer Networking, VoIP Administration, Full-stack Development, Amazon Web Services (AWS), Google Cloud Platform (GCP), Azure, Advisory, Process Development, Engineering

Senior Full-stack Java Developer

2022 - 2023
MUFG Investor Services - Main
  • Provided solutions for the investment industry on a global scale. They offer a range of services, from middle-office outsourcing to custody, fund administration, foreign exchange, and others.
  • Developed features and fixed bugs for a finance web application tool. PrimeNG and Angular 12 are used. Built unit tests for each change, using Jasmine and Karma.
  • Created features and fixed bugs on many Java 11 microservices. Developed unit and integration tests.
  • Created and edited unit and IT test cases, fully complying with scenarios.
  • Made new back-end functionalities and services. Also created a UI with Angular.
  • Resynced an Angular project using its forked version. Created the GitLab rebase branch from a forked repository, using the rebase branch as an upstream on the other project and managing a huge code propagation.
Technologies: Java, Spring Boot, Angular, SSL, Oracle, Amazon Web Services (AWS), ActiveMQ, Docker, Full-stack, JavaScript, CSS, HTML, REST, Postman, Code Review, Back-end, CI/CD Pipelines, TypeScript, GitHub, Test-driven Development (TDD), Finance, Java EE, Serverless Architecture, Containers, Event-driven Architecture, Event-driven Programming, APIs, Back-end Development, Spring Microservice, Back-end Architecture, Spring, MQTT, HTTP REST, Full-stack Development, JavaScript MVC, Engineering, Cloud Architecture

Back-end Developer

2021 - 2022
PhysIQ, Inc.
  • Developed plugins and tools with Python and Kotlin on this platform.
  • Created CI/CD pipelines on GitLab and created scripts.
  • Performed load testing and analyzed the results with the back-end team, identifying improvement points and ensuring the system's actual capacity.
Technologies: Python, Kotlin, Java, Gherkin, Git, Automated Testing, Kubernetes, Google Cloud Platform (GCP), Apache Kafka, Docker, Performance, REST, Load Testing, High-load, Postman, Microservices, Back-end, CI/CD Pipelines, Test-driven Development (TDD), Serverless Architecture, Containers, Event-driven Architecture, Event-driven Programming, Back-end Development, Back-end Architecture, HTTP REST, Data Engineering, ETL, Engineering, Cloud Architecture

Team Lead

2020 - 2022
Turkcell Technology
  • Led the team at the design, implementation, and deployment phases to meet customer expectations for a secure and seamless video conferencing solution. It is a WebRTC-based solution.
  • Assisted with program and project management, along with customer requirement analysis.
  • Managed domestic and foreign team members working remotely, following agile development practices.
  • Built a team with new hire interviews. Attended technical sessions to improve team talents.
  • Investigated open-source solutions and prepared MVP products for demonstration purposes.
  • Attended code review and technical discussion meetings to share experiences.
  • Designed and implemented REST APIs to integrate with third parties, which had their own business logic and wanted to incorporate a video conferencing solution.
Technologies: Java, Spring Boot, WebRTC, Kong, Agile Software Development, Apache Kafka, Redis, NoSQL, Swagger, JVM, Red Hat OpenShift, Architecture, Technical Leadership, Microservices Architecture, OAuth 2, Apache Maven, Leadership, Linux, APIs, IntelliJ IDEA, Performance, Git, Grafana, Kotlin, API Integration, Containerization, Back-end, Single Sign-on (SSO), Docker, Load Testing, Spring, SQL, Apache Tomcat, Postman, Microservices, Kafka Streams, Code Review, Jira, Bitbucket, Hibernate, Pull Requests, REST APIs, Databases, JPA, Message Queues, SOLID Principles, API Development, CI/CD Pipelines, SOAP, Team Leadership, Agile, Twilio API, Technical Hiring, Interviewing, Integration, Spring 5, Prometheus, XMPP, WebSockets, CRM APIs, Jenkins, Software Design, Task Analysis, SSL, Software Architecture, JDBC, Apache Avro, TypeScript, Amazon DynamoDB, Relational Databases, Object-oriented Programming (OOP), Continuous Integration (CI), PostgreSQL, Telecommunications, REST, High-load, AWS Lambda, Amazon RDS, API Gateways, Multitenancy, Java EE, WebLogic, Firebase, Serverless Architecture, Containers, Event-driven Architecture, Event-driven Programming, CTO, Back-end Development, Node.js, Back-end Architecture, Amazon Aurora, HTTP REST, Session Initiation Protocol (SIP), Messaging, Live Chat, Scrum Master, Video Calling, Redis Cache, Stream Processing, Advisory, Scalability, Process Development, Agile Project Management, Engineering, Cloud Architecture

Team Lead

2019 - 2020
Turkcell Technology
  • Managed the instant messaging platform VoIP and services development team in charge of value-added services, chatbots, location-based campaign services, payment features, sending money over the messaging application, and VoIP services.
  • Led the team in the design, implementation, and deployment phases to meet customer expectations.
  • Built a team with new hire interviews. Attended technical sessions to improve the team's technical expertise.
  • Investigated Grafana metrics to find improvement sections for the modules in production. Shared updates with the team and organized and led technical discussions.
  • Deployed media servers over AWS EC2 instances. Subscribers get a better experience by using the closest servers.
  • Designed and implemented REST APIs to integrate with third parties that had their proper business logic and wanted to incorporate a messaging system.
Technologies: Java, Spring Boot, Apache Kafka, Redis, MongoDB, PostgreSQL, VoIP, SIP, Grafana, Amazon EC2, Architecture, Technical Leadership, Microservices Architecture, Apache Maven, Leadership, Linux, APIs, IntelliJ IDEA, Performance, Git, API Integration, Containerization, Back-end, Docker, Load Testing, Spring, SQL, Apache Tomcat, Postman, Microservices, Kafka Streams, Code Review, Jira, Bitbucket, Hibernate, Pull Requests, REST APIs, Databases, JPA, Message Queues, SOLID Principles, API Development, CI/CD Pipelines, SOAP, Team Leadership, Agile, Twilio, Amazon Web Services (AWS), Technical Hiring, Interviewing, Integration, Spring 5, APNs, Prometheus, XMPP, WebSockets, CRM APIs, Full-stack, Software Design, Data Processing, Low Latency, Task Analysis, SSL, Software Architecture, JDBC, Apache Avro, TypeScript, Amazon DynamoDB, Relational Databases, Object-oriented Programming (OOP), Continuous Integration (CI), Telecommunications, REST, High-load, API Gateways, Multitenancy, Java EE, WebLogic, Firebase, Serverless Architecture, AWS Lambda, Event-driven Architecture, Event-driven Programming, CTO, Back-end Development, Chatbots, Back-end Architecture, HTTP REST, Cryptography, Messaging, Live Chat, Scrum Master, Video Calling, Redis Cache, API Platforms, Stream Processing, Advisory, Scalability, Process Development, Agile Project Management, Engineering, Cloud Architecture

Software Architect

2017 - 2019
Turkcell Technology
  • Designed a highly scalable messaging application server.
  • Migrated the project from the Oracle RDBMS to the Apache Cassandra NoSQL database.
  • Coded and designed a push notification server for Apple and Android devices, handling approximately 100,000 TPS notifications.
  • Delivered a solution for usual problems in distributed systems, such as linear scalability, performance utilization, and concurrency.
  • Installed an OpenStack Object Storage server and programmed a client's access, attending a design intent meeting with the engineer from Red Hat.
  • Selected the best technology stack to ensure the application would handle large amounts of traffic quickly and without issues.
Technologies: Java, Spring Boot, Apache Kafka, Redis, Cassandra, Coherence, Apache JMeter, OpenStack Swift, Angular, NoSQL, Flink, Distributed Systems, Architecture, Technical Leadership, Microservices Architecture, Apache Maven, Leadership, Linux, APIs, Python, IntelliJ IDEA, Performance, Git, Grafana, Back-end, JavaScript, Docker, Spring, SQL, Apache Tomcat, Postman, Microservices, Kafka Streams, Code Review, Jira, Bitbucket, Hibernate, Pull Requests, REST APIs, Databases, JPA, Message Queues, SOLID Principles, SQL Stored Procedures, Akka, API Development, CI/CD Pipelines, SOAP, Team Leadership, Agile, Integration, Spring 5, APNs, Prometheus, XMPP, WebSockets, CRM APIs, Full-stack, Software Design, Data Processing, Low Latency, Task Analysis, SSL, Software Architecture, JDBC, Apache Avro, Amazon DynamoDB, Relational Databases, Object-oriented Programming (OOP), Continuous Integration (CI), PostgreSQL, Telecommunications, REST, High-load, API Gateways, Multitenancy, Java EE, WebLogic, Firebase, Serverless Architecture, AWS Lambda, Event-driven Architecture, Event-driven Programming, Back-end Development, Chatbots, Back-end Architecture, HTTP REST, Cryptography, Messaging, Live Chat, Redis Cache, API Platforms, Stream Processing, Scalability, Agile Project Management, Engineering

Senior Software Developer

2014 - 2017
Turkcell Technology
  • Developed a registration server for a messaging application, providing the new generation with instant messaging, voice, and video-call experience.
  • Used custom, internally developed simulator tools and common ones such as JMeter for load testing.
  • Monitored, analyzed, and tuned distributed memory usage.
Technologies: Java, Spring Boot, Apache Kafka, Redis, Cassandra, PostgreSQL, Oracle, Architecture, Microservices Architecture, Apache Maven, Linux, APIs, Python, IntelliJ IDEA, Performance, Git, Grafana, Back-end, Spring, SQL, Apache Tomcat, Postman, Kafka Streams, Code Review, Jira, Bitbucket, Hibernate, Pull Requests, REST APIs, Databases, JPA, Message Queues, SOLID Principles, SQL Stored Procedures, Akka, API Development, SOAP, Spring 5, APNs, Prometheus, XMPP, WebSockets, Software Design, Data Processing, Low Latency, SSL, Software Architecture, JDBC, CSS, Relational Databases, Object-oriented Programming (OOP), Continuous Integration (CI), Telecommunications, REST, High-load, Multitenancy, Java EE, WebLogic, Firebase, Serverless Architecture, Back-end Development, Chatbots, Back-end Architecture, HTTP REST, Data Engineering, ETL, Cryptography, Messaging, Live Chat, Redis Cache, API Platforms, Stream Processing, Scalability, Engineering

Senior Software Developer

2010 - 2014
Nortel Netaş
  • Developed A2, Nortel's VoIP solution implemented and currently maintained by foreign and Turkish engineers. It included over 40,000 Java classes and C codes.
  • Handled the base architecture, including multithreading, JVM performance issues, traffic, and overload conditions.
  • Collaborated with Genband's engineers, formerly Nortel, to implement new features and solve problems.
  • Designed and developed telecommunications and enterprise projects using Java technologies.
  • Developed a UDM project that is a device-change event dispatching system. Built an alarm management system for a secure XML gateway that provides web services from any endpoint and implemented a bulk SMS sender system for enterprise customers.
  • Attended conference calls with product line management, design architects, technical support engineers, and managers to develop the best solutions for customers' needs.
Technologies: Java, Spring Boot, JVM, Performance, Distributed Systems, Multithreading, VoIP, SIP, Oracle, Apache Maven, Linux, IntelliJ IDEA, Back-end, Spring, SQL, Code Review, Jira, Pull Requests, REST APIs, Databases, Message Queues, SOLID Principles, SOAP, Spring 5, Software Design, Low Latency, JDBC, CSS, Relational Databases, Object-oriented Programming (OOP), Telecommunications, REST, High-load, Java EE, WebLogic, Back-end Development, Back-end Architecture, HTTP REST, Session Initiation Protocol (SIP), API Platforms, Engineering

Software Development Support

2006 - 2009
Nortel Netaş
  • Collaborated with Nortel's customers, AT&T and T-Mobile.
  • Identified and solved software, hardware, configuration, and signaling issues on GSM and UMTS systems.
  • Prepared documentation with solutions to be used for similar issues.
Technologies: C, Java, MySQL, Linux, IntelliJ IDEA, Back-end, Software Design, Telecommunications, Java EE, WebLogic

Messaging Platform

https://bip.com/en/
The project is a server-side BiP messaging application that I designed and developed. It gave the new generation an instant messaging, voice, and video-call experience. This platform has millions of users from more than 100 countries and can scale linearly.

I worked on this project as a software developer, architect, and team lead.

Conference Solution

http://www.bipmeet.com
I designed and developed a multi-tenancy conference solution from scratch, leading a team in the design, implementation, and deployment phases to meet customer expectations. I also delivered program and project management and analyzed customer requirements. There were team-building stages and technical interviews that I participated in.

This product comprises many modules, including API interfaces and third-party solutions to manage meetings programmatically. Companies can use the same infrastructure with a private web address and specify user names on a screen. Third-party providers and individuals can view the meeting reports they participated in.

I also completed the payment system integration, allowing customers to buy a private meeting ID via credit card or mobile payment methods.

Mobile Device Management System

The UDM project is a device-change event dispatching system used by GSM operators to track SIM cards and mobile phone changes. I was the development phase leader, overseeing customer meetings and delivering the tools aligned with the most appropriate technologies.

Bulk SMS Platform

A bulk SMS platform project used by GSM operators to send SMS messages. I've contributed to the project as the software development phase leader. The project required high performance in load testing for platform improvement.

Nortel VoIP Platform

http://netas.com.tr/
A2 is Nortel's VoIP solution, currently maintained by foreign and Turkish engineers, including over 40,000 Java classes and C codes.

I collaborated with Genband's engineers to implement new features and solve related problems while handling the base architecture, including multithreading, JVM performance issues, traffic, and overload conditions.

XML Gateway

The Public Integration Box project is a highly secure device and active working redundancy system that provides web services and monitors data over VPN. It consists of IPSEC VPN, a firewall, IDS/IPS, and load balancer components.

I worked on this project as a software development phase leader.

Health Tourism System

A platform that I've designed in collaboration with a teammate to facilitate the appropriate doctor and hospital arrangements for patients coming from abroad. Access to the system is possible via web and mobile terminals, and users are informed of updates via notifications.

Remote Patient Monitoring System

I designed and implemented load test tools in Kotlin and Python. I also created test plans, reports, and scenarios for testing project requirements to ensure the overall quality of the delivered software. Additionally, I worked on the relationship traceability between requirements and test cases, contributing to and assisting in improving test methods and strategies. I also communicated findings to both technical and non-technical audiences.

Automatic Prepaid Payment System

Automatic control of a prepaid payment system used as a tool between prepaid payment firms and operators. The system connects to the web pages of different telecom operators, then scraps and fills form posts automatically from the web page.

Push Notification Platform

The push notification platform was designed and implemented to reach offline users. It applied microservices and async communication paradigms, and the system could scale quickly and linearly. Some platform features include:
• GCM and Firebase Cloud Messaging (FCM) XMPP Connection Server
• APNS TCP and HTTP/2 connection
• Java, Spring Boot, and Kafka
• Message throttling
• Parallel programming
• Grafana and Prometheus

BiP Web GUI

https://web.bip.com
The BiP Web UI is one of the terminals, such as mobile and desktop apps. The project involved designing and implementing the web UI parallel work with users' mobile devices and handling the WebSocket connection. I also used Angular as a web framework.

BiP Discover Management Console

https://discover.bip.com
A corporate customer administrator panel with diverse functionalities, including a super admin that can create and activate new corporate customers. It was a full-stack project that used Angular as a web framework. I also handled role management and the customer management portal.

Database Migration Project

A database migration project of millions of users' roster data from RDBMS to NoSQL on the fly, without any service interruption. It involved redesigning the tables in terms of needs for the NoSQL tech stack and coding a scala job to retrieve data in RDBMS and then create it in SSTable format.

Reconciliation Application

Implemented solutions for the investment industry on a global scale. They offer a range of services, from middle-office outsourcing to custody, fund administration, foreign exchange, and others.

I created new back-end functionalities and services.
I made back-end services implemented in terms of microservices concept.
ActiveMQ and Feignclient are used for intercommunication
The UI is created by Angular 12.
For identity services, Keycloak is used to create users and services with a range of roles.

Messaging App Similar to WhatsApp Business

https://api.ayoba.me/business/api-docs/
I created a messaging platform with functionalities similar to WhatsApp Business.

FEATURES
• 3rd-parties can consume APIs.
• Security flows were designed to include JWT roles, HMAC, initial registration, etc.
• A linearly scalable platform handling high messaging throughput.
2006 - 2008

Master's Degree in Computer Engineering

Marmara University - Istanbul, Turkey

2001 - 2006

Bachelor's Degree in Computer Engineering

Karadeniz Technical University - Trabzon, Turkey

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Data Analyst Nanodegree

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MARCH 2013 - PRESENT

Java Performance Tuning and Optimization

Oracle

Libraries/APIs

REST APIs, API Development, JDBC, Lombok, WebRTC, Node.js, Twilio API, JMS, GCM

Tools

IntelliJ IDEA, Git, Grafana, Kafka Streams, Jira, Bitbucket, Kong, Apache Tomcat, Postman, Apache Maven, GitLab CI/CD, GitLab, Gradle, Cucumber, GitHub, MQTT, Slack, Apache JMeter, Flink, NGINX, Jenkins, Firebase Cloud Messaging (FCM), Apache Avro, ChatGPT, Keycloak, ActiveMQ, Google Kubernetes Engine (GKE), Android Jetpack, Amazon Simple Queue Service (SQS), Amazon Simple Notification Service (Amazon SNS)

Frameworks

Spring Boot, Spring 4, Spring, Angular, JNI, Hibernate, JPA, OAuth 2, Spring Microservice, JavaScript MVC, Swagger, Ionic, Bootstrap, JUnit, Mockito, Akka, Spring 5

Languages

Java, SQL, C, Python, Kotlin, JavaScript, TypeScript, HTML, Python 3, Java 7, PHP, Gherkin, Scala, CSS

Paradigms

Agile Software Development, REST, Load Testing, Microservices, Object-oriented Programming (OOP), Serverless Architecture, Event-driven Architecture, Event-driven Programming, Back-end Architecture, Agile Project Management, Parallel Programming, Agile, Microservices Architecture, Test-driven Development (TDD), Unit Testing, Automated Testing, Continuous Integration (CI), Data Science, ETL

Platforms

JVM, Apache Kafka, Java EE, Linux, Docker, Amazon Web Services (AWS), AWS Lambda, Firebase, Oracle, Red Hat OpenShift, Apache Flink, OpenShift, Mobile, Twilio, Amazon EC2, Kubernetes, Google Cloud Platform (GCP), Android, Azure

Storage

Redis, Relational Databases, Redis Cache, MySQL, Cassandra, PostgreSQL, NoSQL, Databases, Amazon DynamoDB, Amazon Aurora, MongoDB, SQL Stored Procedures, Google Cloud

Industry Expertise

Telecommunications, Project Management, Healthcare

Other

Software Development, Performance, Multithreading, VoIP, Leadership, APIs, Code Review, Message Queues, SOLID Principles, Back-end, Technical Leadership, Architecture, Communication, SOAP, Source Code Review, Technical Hiring, Interviewing, Integration, API Integration, CRM APIs, Software Design, Low Latency, Task Analysis, Software Architecture, WebLogic, Back-end Development, HTTP REST, Messaging, Live Chat, API Platforms, Advisory, Scalability, Process Development, Engineering, Java Native Interface (JNI), Distributed Systems, SIP, Coherence, SMS, Pull Requests, Scripting, Full-stack, Team Leadership, Containerization, WebSockets, Data Processing, SSL, Amazon RDS, API Gateways, Multitenancy, Containers, CTO, Session Initiation Protocol (SIP), Full-stack Development, Cryptography, Scrum Master, Video Calling, Stream Processing, Cloud Architecture, OpenStack Swift, Payment APIs, IPsec, IDS/IPS, High-load, CI/CD Pipelines, Predictive Modeling, Data Wrangling, Probability Theory, Chatbots, Open Source, Statistics, Web Scraping, HTTP, APNs, Prometheus, XMPP, Single Sign-on (SSO), Finance, OpenAI, Artificial Intelligence (AI), Lambda Functions, Serverless, Data Engineering, Peer-to-peer Networking, VoIP Administration

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