Thomas Kountis
Senior Software Engineer at Apple
San Jose, California, United States
Summary
🤩
Rockstar🎓
Top SchoolThomas Kountis is a Senior Software Engineer in San Jose with 11 years of professional experience and over 14 years of personal practice building high-performance, distributed systems in JVM and other ecosystems. At Apple he contributes to core JVM frameworks like ServiceTalk and Netty, and is an active open-source contributor to notable projects such as servicetalk and Hazelcast, where he implemented HyperLogLog-based Cardinality Estimator and improved distributed scheduled execution. He brings deep backend and performance-engineering expertise from roles at Hazelcast, AOL, and IBM, spanning Java, Erlang, and systems-level optimizations including off-heap data structures. Known for a “whatever it takes” attitude, he pairs hands-on coding with architecture and operational improvements to reduce latency and increase throughput. Colleagues rely on him to dive under the hood of complex systems and deliver pragmatic, resilient solutions in production.
11 years of coding experience
11 years of employment as a software developer
Bachelor of Science (BSc), Computer Science, Bachelor of Science (BSc), Computer Science at Queen Mary, U. of London
English, Greek
Stackoverflow
169reputation
21kreached
9answers
0questions
Github Skills (15)
hazelcast10
javas10
http10
distributed-systems10
netty10
hyperloglog10
java10
grpc10
testing9
eclipse6
javascript6
jquery6
svn6
subclipse6
garbage-collection6
Programming languages (6)
Github contributions (5)
apple/servicetalk
Aug 2020 - Aug 2022
A networking framework that evolves with your application
Role in this project:
Back-end Developer
Back-end DeveloperContributions:10 releases, 666 reviews, 91 commits in 1 year 11 months
Contributions summary:Thomas primarily focused on enhancing the `servicetalk` project's gRPC and HTTP capabilities, with changes spanning several areas. Key contributions included implementing gRPC message-encoding support, providing more informative exceptions for gRPC calls, and addressing issues with HTTP content encoding in H1 & H2 protocols. The user also contributed to improving the handling of trailers, fixing issues with content length calculations, and consolidating HTTP codecs with gRPC.
rpcgrpchttp2frameworkreactive-streams
hazelcast/hazelcast
Sep 2016 - Apr 2020
Hazelcast is a unified real-time data platform combining stream processing with a fast data store, allowing customers to act instantly on data-in-motion for real-time insights.
Role in this project:Backend Developer
Backend DeveloperContributions:160 commits, 326 PRs, 133 pushes in 3 years 7 months
Contributions summary:Thomas implemented a Cardinality Estimator service using HyperLogLog, making it available through a HazelcastInstance. The commits indicate the user added features for permissions related to the CardinalityEstimator, along with enhancements for the Distributed Scheduled Executor Service, adding support for missing permission types. Further work was done to improve HyperLogLog coverage and fix a bug in Sparse to Dense conversion and fixing an issue with task completion and re-execution.
computationstream-processingbigtablereal-timestreaming-data
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