Explain the internal working of Selenium's explicit wait polling mechanism?

WebDriverWait is built on a lower-level FluentWait, which runs a loop that repeatedly invokes the supplied condition function against the driver, sleeping for a fixed polling interval (500ms by default) between each attempt.

flowchart TD
    A[wait.until condition called] --> B[Evaluate condition function]
    B --> C{Condition true?}
    C -->|Yes| D[Return result immediately]
    C -->|No| E{Timeout elapsed?}
    E -->|No| F[Sleep polling interval]
    F --> B
    E -->|Yes| G[Throw TimeoutException]

Each poll re-evaluates the condition from scratch, so a condition like elementToBeClickable genuinely re-runs its underlying findElement and state checks on every single iteration rather than checking once and caching. By default, transient exceptions like NoSuchElementException thrown mid-poll are silently ignored so the loop can keep retrying, but FluentWait.ignoring() controls exactly which exception types get swallowed this way versus immediately propagating and aborting the wait.