Design a Fixed Size Thread Pool in Java | Concurrency LLD Interview
If you’re preparing for Low Level System Design interviews, there’s one concurrency question that appears again and again:
Design a Thread Pool.
Most developers know how to use Executors.newFixedThreadPool(), but interviews don’t test convenience — they test understanding. In this video, we break down how a thread pool actually works under the hood and build one from scratch to truly understand Java concurrency.
In this deep dive, you’ll learn:
• How ThreadPoolExecutor really manages threads and queues
• The role of corePoolSize, maximumPoolSize, and keepAliveTime
• Why a BlockingQueue sits at the heart of thread pool design
• How rejection policies provide backpressure in high load systems
• The internal worker thread loop that powers Java thread pools
We’ll also implement a simplified custom thread pool step by step using a bounded BlockingQueue and worker threads. This will help you understand the producer-consumer model, task scheduling, and graceful shutdown — concepts that frequently appear in LLD interviews and real production systems.
This video is the first part of a new series on Low Level System Design problems with a focus on concurrency patterns used in real backend systems.
If you’re a backend engineer preparing for interviews or trying to master Java concurrency, this series is for you.
Subscribe to CodeGranular for deep dives into:
Java internals, concurrency patterns, Kafka, distributed systems, and high-performance backend engineering. 🐼⚡
What concurrency interview questions have you faced recently? Let me know in the comments.
#Java
#JavaConcurrency
#ThreadPool
#ThreadPoolExecutor
#LLDInterview
#SystemDesign
#LowLevelDesign
#BackendEngineering
#ConcurrencyInJava
#SoftwareEngineering
#JavaMultithreading
#Programming
#TechInterviews
On this page of the site you can watch the video online Design a Fixed Size Thread Pool in Java | Concurrency LLD Interview with a duration of hours minute second in good quality, which was uploaded by the user Code Granular 09 March 2026, share the link with friends and acquaintances, this video has already been watched 55 times on youtube and it was liked by 2 viewers. Enjoy your viewing!
