@Override
    Backoff doBuild() {
        return new FixedBackoff(delayMillis);
    }
Sets the delay duration in milliseconds for the Fixed {@link Backoff}.

<p>This value determines the fixed amount of time the backoff will delay
before retrying an operation.</p>

@param delayMillis the delay in milliseconds
core/src/main/java/com/linecorp/armeria/client/retry/FixedBackoffBuilder.java