Implementarea unui Rate Limiter

public class RateLimiter {
    private static final int ONE_SECOND = 1000;
    private final Map<String, List<Long>> requests;
    private boolean enabled = false;
    private int requestsPerSecond;

    public RateLimiter(Environment environment) {
        requests = new HashMap<>();
        if (environment.getProperty("enable.rate.limiter") != null) {
            this.enabled = Boolean.parseBoolean(environment.getProperty("enable.rate.limiter"));
        }
        if (this.enabled) {
            String property = environment.getProperty("max.requests.per.user.per.second");
            Assert.notNull(property, "Max requests per second not defined!");
            this.requestsPerSecond = Integer.parseInt(property);
        }
    }

    public boolean allows(String ipAddress) {
        if (!enabled) {
            return true;
        }

        if (!requests.containsKey(ipAddress)) {
            requests.put(ipAddress, new ArrayList<>());
        }

        Long now = System.currentTimeMillis();
        cleanup(ipAddress, now);
        requests.get(ipAddress).add(now);

        return requests.get(ipAddress).size() <= requestsPerSecond;
    }

    private void cleanup(String ipAddress, Long now) {
        List<Long> markedForDeletion = new ArrayList<>();
        for (Long timestamp : requests.get(ipAddress)) {
            if (now - timestamp > ONE_SECOND) {
                markedForDeletion.add(timestamp);
            }
        }
        requests.get(ipAddress).removeAll(markedForDeletion);
    }
}