High Concurrency and Multithreading: Core Technologies and Practices

High concurrency refers to a large number of client requests arriving at the server simultaneously, such as 100,000 order requests at 12:00 AM during a major sales event.

Key metrics for evaluating high concurrency include the number of concurrent users, TPS (Transactions Per Second), and QPS (Queries Per Second).

Multithreading is the technique of using multiple executors to handle the same type of task at the same time, for example 100 threads processing 2,000 order requests concurrently.

Concurrency involves multiple threads operating on the same resources, requiring thread‑safety and efficient resource utilization.

Core Multithreading Technologies

Java threads

Thread model

Java thread pool

Future (various Future implementations)

Fork/Join framework

volatile keyword

CAS (compare‑and‑swap) atomic operations

AQS (AbstractQueuedSynchronizer) concurrency framework

synchronized (monitor lock)

Concurrent queues (blocking queues)

Core High‑Concurrency Technologies

Distributed cache technologies represented by Redis

Distributed message queue technologies represented by Kafka

NoSQL data technologies represented by MongoDB

Microservice architecture technologies represented by Dubbo

Database sharding and partitioning technologies represented by TDDL

Load balancing technologies represented by Nginx

Server monitoring, security, and disaster‑recovery techniques

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