Halil Ayyildiz, Developer in Amsterdam, Netherlands
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Halil Ayyildiz

Verified Expert  in Engineering

Software Developer

Amsterdam, Netherlands
Toptal Member Since
October 22, 2020

With more than a decade of professional experience, Halil is a software developer with in-depth and broad expertise in back-end systems and cloud services. He also has hands-on experience in the reliability and scalability of planet-scale cloud systems. Halil is a lifelong learner and software expert who chooses the proper tools and algorithms to best solve business problems.


Google Cloud Platform (GCP)
Redis, Amazon Web Services (AWS), NoSQL, Cucumber, Java 11, API Integration...
Redis, NoSQL, RabbitMQ, API Integration, REST APIs, Oracle, TypeScript...




Preferred Environment

Cloud, Linux, IntelliJ IDEA, Kubernetes, Java

The most amazing...

...project I've contributed to was Google Cloud Platform, improving the reliability of top cloud customers.

Work Experience

Software Developer

2022 - PRESENT
  • Identified and improved reliability metrics for top cloud customers.
  • Contributed to planet-scale tools that monitor and improve the reliability metrics of cloud customers.
  • Developed workflows to monitor and calculate the SLO performance of top cloud customers.
Technologies: Google Cloud Platform (GCP)

Senior Software Developer

2018 - 2022
  • Developed APIs for developers which provide information about places in TomTom-powered maps, libraries, applications, and services worldwide and are published at Developer.tomtom.com/search-api.
  • Built four new microservices from scratch, including parking spaces, fuel prices, Rich POI, and charging availability services.
  • Improved data release duration from more than eight hours to two hours by optimizing the data storage method and storing data in an embedded database (RocksDB) instead of a file system-based structure.
  • Switched the infrastructure from an Azure VM-based custom solution to an AKS (Azure Kubernetes Service) based one, which decreases cost and improves the reliability of the services.
  • Designed a processing pipeline for regularly fetching and parsing Foursquare data and incorporating it into the TomTom Rich POI service.
  • Supported the product owner with the design of API fields to maintain the readability of the response and flexibility for further changes.
Technologies: Redis, Amazon Web Services (AWS), NoSQL, Cucumber, Java 11, API Integration, REST APIs, Microservices, Jira, Protobuf, gRPC, Gatling Load Testing, Karate API Testing, Jenkins, Apache Maven, Spring Boot, Java, Helm, Docker, Kubernetes, Terraform, Azure, Node.js, Back-end Development, Apache Kafka, TypeScript, SQL, APIs, Git, Memcached, GraphQL

Senior Software Engineer and Technical Lead

2012 - 2018
  • Managed the software development activities of a team of five to seven developers using Agile software development methodologies for the projects executed in several countries, including Turkey, Austria, Saudi Arabia, Spain, and Norway.
  • Developed an outage management system that detects and manages electricity outages in smart grid networks and integrates with the electricity distribution company's ERP systems.
  • Guided the software development team that developed the core components, such as outage management and mobile outage management system, and built the integration with customer systems, including SAP PM, SAP WFM, and SAP CRM.
  • Participated actively in technical customer-facing meetings to collect requirements and decide design approaches.
  • Supported external projects in other countries, such as requirements collection in Spain and the implementation of the outage management module in Norway.
  • Proposed new ideas to deal with customer requests in modeling low voltage network model of utility companies with more than two million customer feeding points.
  • Introduced innovative extensions to an outage management system, such as a mobile application for customers. The source code for a simple prototype can be found at github.com/halilayyildiz/outagetracker.
Technologies: Redis, NoSQL, RabbitMQ, API Integration, REST APIs, Oracle, TypeScript, Spring Integration, Spring, Spring Data JPA, Node.js, Angular, JavaScript, Java, Back-end Development, Amazon Web Services (AWS), Kubernetes, SQL, APIs, Git

Software Development Engineer

2010 - 2012
  • Developed a data augmentation engine that augments any given text content by using linked data sources and semantic web technologies.
  • Implemented linked data vocabulary, information extraction, text mining algorithms, such as NER, WSD, and more, and recommendation system algorithms like collaborative filtering.
  • Contributed to an open-source software project, DBpedia, by implementing mappings for Turkish Wikipedia: Mappings.dbpedia.org/index.php/Mapping_tr.
  • Published a whitepaper and presented it at Proceeding SWIM '11 Proceedings of the International Workshop on Semantic Web Information Management in Athens, Greece: Dl.acm.org/doi/10.1145/1999299.1999305.
Technologies: REST APIs, RDF, OWL, MySQL, jQuery, Spring, Java, Back-end Development, SQL, APIs, Git, Memcached

Back-end Software Developer

2008 - 2009
Sebit A.S.
  • Contributed to the Vitamin project back-end team, which serves online educational content, such as animations, learning objects, games, exams, and so on, to 800,000+ users.
  • Implemented an online testing platform where 100,000+ students take online tests concurrently and calculate the results afterward.
  • Developed web-based online education components on top of a distributed, scalable, and fault-tolerant infrastructure.
Technologies: REST APIs, Apache Maven, JavaScript, PostgreSQL, HTML, Java, Back-end Development, SQL, Git, Memcached

TomTom Search API

Developed four new microservices from scratch and was responsible for the products from end to end, from software design to final deployment, including on-call duty. I've made a remarkable impact on the cost optimization of the cloud environment without sacrificing service availability.

TomTom has a broad list of location technology products. One major group is the search product unit, responsible for providing online search services on the top of map data.

I've been working on the search product unit to provide extended search APIs to the customers. Those APIs cover a list of different capabilities, including parking space availability, fuel prices, electric vehicle charging station availability, and rich data services. All of these products are available worldwide via highly available, distributed, resilient cloud deployments located in multiple geographical regions to serve low latency APIs to the customers. These services are being used by cars and Azure maps back-end developers who have acquired the developer API key via the TomTom developer portal.

Siemens OMS | Outage Management System

Siemens Outage Management System is an on-premise software solution for utility companies that tracks outages in the electricity network, providing full lifecycle management of the outages, starting from outage detection on the grid up to report generation for power loss calculations of the customers.

I managed a team of five to six developers. We handled the extension of the global product according to local market rules. We also implemented the integration layer for external ERP systems, including SAP-PM, SAP CRM, SAP WFM, and smart meters. I actively participated in the collection of customer requirements and the design and development of the product. I also designed an integration medium that supports two-way communication between the OMS and customer ERP systems.

I've successfully delivered and customized OMS to four different utility companies in Turkey and one another in Saudi Arabia. Moreover, I've supported Siemens branches in Spain and Norway for their local OMS solutions.

At the end of these projects, I successfully designed the outage management workflow and reduced response time and average outage duration of reported failures. I also generated monthly and yearly reports that comply with local regulations.
2011 - 2013

Master's Degree in Software Engineering

Middle East Technical Univesity - Ankara, Turkey

2004 - 2008

Bachelor's Degree in Computer Engineering

Middle East Technical Univesity - Ankara, Turkey


Certified Professional for Software Architecture

International Software Architecture Qualification Board (ISAQB)


Node.js, REST APIs, jQuery, Protobuf


Gatling Load Testing, Karate API Testing, Apache Maven, Git, IntelliJ IDEA, Cucumber, Terraform, Jenkins, Helm, RabbitMQ, Jira, SoapUI


Spring, Spring Boot, gRPC, Angular, Spring Integration


Java, SQL, JavaScript, TypeScript, HTML, Java 11, OWL, RDF, GraphQL




Azure, Kubernetes, Docker, Oracle Database, Amazon Web Services (AWS), Oracle, Apache Kafka, Linux, Google Cloud Platform (GCP)


Redis, Memcached, PostgreSQL, MySQL, RocksDB, NoSQL, Spring Data JPA


Cloud, RESTful Web Services, API Integration, Back-end Development, APIs, XML Web Services

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