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What is Temporal?

Temporal is a scalable and reliable runtime for Reentrant Processes called Temporal Workflow Executions.

Temporal's tenth rule

Any sufficiently complex distributed system contains an ad-hoc, informally-specified, bug-ridden, slow implementation of half of temporal.io.

The Temporal system

The Temporal system
  • π = Workflow Execution

Temporal Application

A Temporal Application is a set of Temporal Workflow Executions (Π). Each Temporal Workflow Execution (π) has exclusive access to its local state, executes concurrently to all other Workflow Executions, and communicates with other Workflow Executions and the environment via message passing.

A Temporal Application can consist of millions to billions of Workflow Executions. Workflow Executions are lightweight components. A Workflow Execution consumes few compute resources; in fact, if a Workflow Execution is suspended, such as when it is in a waiting state, the Workflow Execution consumes no compute resources at all.

Reentrant Process

A Temporal Workflow Execution is a Reentrant Process. A Reentrant Process is resumable, recoverable, and reactive.

  • Resumable: Ability of a process to continue execution after execution was suspended on an awaitable.
  • Recoverable: Ability of a process to continue execution after execution was suspended on a failure.
  • Reactive: Ability of a process to react to external events.

Therefore, a Temporal Workflow Execution executes a Temporal Workflow Definition, also called a Temporal Workflow Function, your application code, exactly once and to completion—whether your code executes for seconds or years, in the presence of arbitrary load and arbitrary failures.

Temporal runtime

The Temporal runtime consists of the Temporal Server and Worker Processes. A Temporal SDK provides users with the APIs they need to write Workflow Definitions as well as the APIs to invoke Workflow Executions and invoke Worker Processes.