Synchronous
A communication model where the caller waits for the operation to complete before moving on. Simpler to reason about but blocks the thread.
What is Synchronous?
A communication model where the caller waits for the operation to complete before moving on. Simpler to reason about but blocks the thread.
Synchronous is a foundational concept that sits in the Core Fundamentals area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "Synchronous" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
Learn Synchronous in depth
Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the Synchronous lessonRelated lessons
Lessons that touch on Synchronous as part of a larger topic.
Synchronous Replication
Wait for replicas to confirm before acknowledging writes, zero data loss at the cost of latency
intermediate · data replication distribution
Request-Response Pattern
The most fundamental messaging pattern, send a request, wait for a reply
intermediate · messaging event systems
Synchronous Processing
Sequential request-response pattern where each operation waits for the previous one
foundation · core fundamentals
Asynchronous Processing
Non-blocking concurrent operations that don't wait for each other
foundation · core fundamentals
Asynchronous Replication
The default replication mode, fast writes at the cost of potential data loss
intermediate · data replication distribution
See also
Related glossary terms you might want to look up next.
Asynchronous
A communication model where the caller fires off a request and continues without waiting for a response. Essential for non-blocking I/O and event-driven systems.
Latency
The time delay between sending a request and getting a response. Amazon found every 100ms of extra latency costs 1% in sales.
Throughput
The number of operations a system can handle per unit of time. Think of it as how many cars a highway can move per hour.