public TokenBucketThrottlingStrategyBuilder<T> minimumBackoff(Duration minimumBackoff) {
        requireNonNull(minimumBackoff, "minimumBackoff");
        checkArgument(!minimumBackoff.isNegative(), "minimumBackoff: %s (expected: >= 0)", minimumBackoff);
        this.minimumBackoff = minimumBackoff;
        return this;
    }
Optional {@link Duration} that defines a minimum backoff period for throttled requests.
By default, it will be set to 0 seconds.
bucket4j/src/main/java/com/linecorp/armeria/server/throttling/bucket4j/TokenBucketThrottlingStrategyBuilder.java