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Technical Vocabularynoun · /kənˈkɜːrənsi/

concurrency

In simple English

In software engineering, concurrency is a fundamental concept that allows programs to manage multiple operations that may overlap in time. This does not necessarily mean operations happen simultaneously (that would be parallelism), but rather that they can be interleaved and progress independently. Concurrency is critical for building responsive applications, handling multiple user requests on servers, and maximizing resource efficiency. For example, a web server uses concurrency to serve multiple clients at once, even if it has limited CPU cores. Developers must understand concurrency because it introduces challenges like race conditions, deadlocks, and synchronization issues. In modern tech workplaces, discussions about concurrency often involve threading, async programming, message queues, and distributed systems. Different programming languages and frameworks provide different mechanisms to handle concurrency, from threads and locks to async-await patterns and actor models.

Understanding how systems handle multiple operations simultaneously or quasi-simultaneously in programming.

At a glanceCEFR C1
Commonness4/5
Versatility4/5
FormalityCasualFormalFormal
Spoken ↔ WrittenSpokenWrittenBoth
Directness ↔ DiplomaticDirectDiplomaticNeutral
RegionUS and UK
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Say it like this

✓We need better concurrency handling in the API.
✓The system lacks proper concurrency control.
✓Concurrency issues caused the race condition.

Real examples

in a standup

"We discovered a concurrency bug where two threads were updating the same database record simultaneously."

in a code review

"This implementation improves concurrency by using message queues instead of shared memory."

in a team meeting

"Our node server handles high concurrency through async-await patterns rather than traditional threading."

Don't say this

Handle with care. Do not confuse concurrency with parallelism. Concurrency means tasks can progress independently, while parallelism means tasks execute at exactly the same time on multiple processors.

✕We need more concurrency in our application.
✓We need to improve concurrency handling in our application.— Concurrency is a property of the system design, not something you have more or less of; you improve how you manage it.
✕Concurrency and parallelism are the same thing.
✓Concurrency and parallelism are related but different concepts.— Concurrency allows multiple tasks to progress; parallelism means they execute at the exact same moment on different cores.
✕We concurrency the code.
✓We implemented concurrency in the code.— Concurrency is a noun; you do not use it as a verb directly.

Other forms

noun

concurrency

"The system handles concurrency through thread pools."

adjective

concurrent

"We are running concurrent processes on multiple servers."

adverb

concurrently

"Multiple requests are processed concurrently by the application."

Often used with

handle concurrencyTo manage multiple simultaneous operations in a system.
concurrency controlMechanisms to ensure safe concurrent access to shared resources.
concurrency issue / bugProblems that arise from improper handling of concurrent operations.
concurrency modelThe approach or framework a system uses to manage concurrent tasks.
improve / optimize concurrencyTo make the system better at handling multiple operations efficiently.

Similar words

parallelismRelated but different: parallelism means simultaneous execution on multiple processors, while concurrency means overlapping progress.
multitaskingSimilar concept in operating systems, but concurrency is more precise in software development contexts.
asynchronous processingOne technique used to achieve concurrency, but concurrency is the broader concept.

Opposites

sequential executionsynchronous processing

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Practice

Try it

4 quick exercises

Pick the most natural phrasing

1. Your team needs to fix problems with multiple database updates happening at once. Which phrasing is most professional?

Complete the sentence

2. The microservices architecture improved _______ by allowing multiple requests to be processed independently.

Spot the mistake

3. Which sentence uses concurrency correctly?

Rewrite naturally

4. Rewrite in natural tech English: 'Our server can do many things at the same time without waiting for each one to finish.'

Questions

Quick poll

Have you said "concurrency" in a standup this week?

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