diff --git a/src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java b/src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java
index 32c2aba..1cdb717 100644
--- a/src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java
+++ b/src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java
@@ -10,6 +10,7 @@
 
 import redis.clients.jedis.Jedis;
 import redis.clients.jedis.JedisPool;
+import redis.clients.jedis.Transaction;
 
 public class SiteStatsDaoRedisImpl implements SiteStatsDao {
 
@@ -47,7 +48,7 @@ public void update(MeterReading reading) {
 			ZonedDateTime day = reading.getDateTime();
 			String key = RedisSchema.getSiteStatsKey(siteId, day);
 
-			updateBasic(jedis, key, reading);
+			updateOptimized(jedis, key, reading);
 		}
 	}
 
@@ -81,6 +82,18 @@ private void updateBasic(Jedis jedis, String key, MeterReading reading) {
 	// Challenge #3
 	private void updateOptimized(Jedis jedis, String key, MeterReading reading) {
 		// START Challenge #3
+		try (Transaction t = jedis.multi()) {
+			String reportingTime = ZonedDateTime.now(ZoneOffset.UTC).toString();
+			t.hset(key, SiteStats.reportingTimeField, reportingTime);
+			t.hincrBy(key, SiteStats.countField, 1);
+			t.expire(key, weekSeconds);
+
+			compareAndUpdateScript.updateIfGreater(t, key, SiteStats.maxWhField, reading.getWhGenerated());
+			compareAndUpdateScript.updateIfLess(t, key, SiteStats.minWhField, reading.getWhGenerated());
+			compareAndUpdateScript.updateIfGreater(t, key, SiteStats.maxCapacityField, getCurrentCapacity(reading));
+
+			t.exec();
+		}
 		// END Challenge #3
 	}