diff --git a/tools/asynq/cmd/migrate.go b/tools/asynq/cmd/migrate.go
index f9e048b..28c3819 100644
--- a/tools/asynq/cmd/migrate.go
+++ b/tools/asynq/cmd/migrate.go
@@ -104,49 +104,13 @@ func migrate(cmd *cobra.Command, args []string) {
 	fmt.Print("Done\n")
 
 	fmt.Print("Updating to new schema...")
-	// All list/zset should contain task-ids and store task data under task key
-	// - Unmarshal using old task schema
-	// - Marshal data using new schema
-
 	for _, qname := range queues {
-		// Active Tasks + Deadlines set
-
-		// Pending Tasks
-		data, err := r.Client().LRange(backupKey(base.PendingKey(qname)), 0, -1).Result()
-		failIfError(err, "Failed to read backup pending key")
-
-		for _, s := range data {
-			msg, err := UnmarshalOldMessage(s)
-			failIfError(err, "Failed to unmarshal message")
-
-			if msg.UniqueKey != "" {
-				ttl, err := r.Client().TTL(msg.UniqueKey).Result()
-				failIfError(err, "Failed to get ttl")
-
-				if ttl > 0 {
-					err = r.Client().Del(msg.UniqueKey).Err()
-					logIfError(err, "Failed to delete unique key")
-				}
-
-				// Regenerate unique key.
-				msg.UniqueKey = base.UniqueKey(msg.Queue, msg.Type, msg.Payload)
-				if ttl > 0 {
-					err = r.EnqueueUnique(msg, ttl)
-				} else {
-					err = r.Enqueue(msg)
-				}
-				failIfError(err, "Failed to enqueue pending message")
-
-			} else {
-				err := r.Enqueue(msg)
-				failIfError(err, "Failed to enqueue pending message")
-			}
-		}
-
+		// TODO: Deadlines set
+		updateListMessages(r.Client(), base.ActiveKey(qname), "active")
+		updateListMessages(r.Client(), base.PendingKey(qname), "pending")
 		updateZSetMessages(r.Client(), base.ScheduledKey(qname), "scheduled")
 		updateZSetMessages(r.Client(), base.RetryKey(qname), "retry")
 		updateZSetMessages(r.Client(), base.ArchivedKey(qname), "archived")
-
 	}
 	fmt.Print("Done\n")
 
@@ -247,6 +211,148 @@ func DecodeMessage(s string) (*OldTaskMessage, error) {
 	return &msg, nil
 }
 
+// Input:
+// KEYS[1] -> asynq:{<qname>}:t:<task_id>
+// KEYS[2] -> asynq:{<qname>}:pending
+// --
+// ARGV[1] -> task message data
+// ARGV[2] -> task ID
+// ARGV[3] -> task timeout in seconds (0 if not timeout)
+// ARGV[4] -> task deadline in unix time (0 if no deadline)
+// ARGV[5] -> task state (oneof "active", "pending")
+//
+// Output:
+// Returns 1 if successfully enqueued
+var taskLPushCmd = redis.NewScript(`
+redis.call("HSET", KEYS[1],
+           "msg", ARGV[1],
+           "state", ARGV[5],
+           "timeout", ARGV[3],
+           "deadline", ARGV[4])
+redis.call("LPUSH", KEYS[2], ARGV[2])
+return 1
+`)
+
+// Enqueue adds the given task to the pending list of the queue.
+func LPushTask(c redis.UniversalClient, key string, msg *base.TaskMessage, state string) error {
+	encoded, err := base.EncodeMessage(msg)
+	if err != nil {
+		return err
+	}
+	if err := c.SAdd(base.AllQueues, msg.Queue).Err(); err != nil {
+		return err
+	}
+	keys := []string{
+		base.TaskKey(msg.Queue, msg.ID.String()),
+		key,
+	}
+	argv := []interface{}{
+		encoded,
+		msg.ID.String(),
+		msg.Timeout,
+		msg.Deadline,
+		state,
+	}
+	return taskLPushCmd.Run(c, keys, argv...).Err()
+}
+
+// KEYS[1] -> unique key
+// KEYS[2] -> asynq:{<qname>}:t:<taskid>
+// KEYS[3] -> asynq:{<qname>}:pending
+// --
+// ARGV[1] -> task ID
+// ARGV[2] -> uniqueness lock TTL
+// ARGV[3] -> task message data
+// ARGV[4] -> task timeout in seconds (0 if not timeout)
+// ARGV[5] -> task deadline in unix time (0 if no deadline)
+// ARGV[6] -> task state (oneof "active", "pending")
+//
+// Output:
+// Returns 1 if successfully enqueued
+// Returns 0 if task already exists
+var taskLPushUniqueCmd = redis.NewScript(`
+local ok = redis.call("SET", KEYS[1], ARGV[1], "NX", "EX", ARGV[2])
+if not ok then
+  return 0
+end
+redis.call("HSET", KEYS[2],
+           "msg", ARGV[3],
+           "state", ARGV[6],
+           "timeout", ARGV[4],
+           "deadline", ARGV[5],
+           "unique_key", KEYS[1])
+redis.call("LPUSH", KEYS[3], ARGV[1])
+return 1
+`)
+
+func LPushTaskUnique(c redis.UniversalClient, key string, msg *base.TaskMessage, state string, ttl time.Duration) error {
+	encoded, err := base.EncodeMessage(msg)
+	if err != nil {
+		return err
+	}
+	if err := c.SAdd(base.AllQueues, msg.Queue).Err(); err != nil {
+		return err
+	}
+	keys := []string{
+		msg.UniqueKey,
+		base.TaskKey(msg.Queue, msg.ID.String()),
+		key,
+	}
+	argv := []interface{}{
+		msg.ID.String(),
+		int(ttl.Seconds()),
+		encoded,
+		msg.Timeout,
+		msg.Deadline,
+		state,
+	}
+	res, err := taskLPushUniqueCmd.Run(c, keys, argv...).Result()
+	if err != nil {
+		return err
+	}
+	n, ok := res.(int64)
+	if !ok {
+		return errors.E(errors.Internal, fmt.Sprintf("unexpected return value from Lua script: %v", res))
+	}
+	if n == 0 {
+		return errors.E(errors.AlreadyExists, errors.ErrDuplicateTask)
+	}
+	return nil
+}
+
+func updateListMessages(c redis.UniversalClient, key, state string) {
+	data, err := c.LRange(backupKey(key), 0, -1).Result()
+	failIfError(err, "Failed to read backup pending key")
+
+	for _, s := range data {
+		msg, err := UnmarshalOldMessage(s)
+		failIfError(err, "Failed to unmarshal message")
+
+		if msg.UniqueKey != "" {
+			ttl, err := c.TTL(msg.UniqueKey).Result()
+			failIfError(err, "Failed to get ttl")
+
+			if ttl > 0 {
+				err = c.Del(msg.UniqueKey).Err()
+				logIfError(err, "Failed to delete unique key")
+			}
+
+			// Regenerate unique key.
+			msg.UniqueKey = base.UniqueKey(msg.Queue, msg.Type, msg.Payload)
+			if ttl > 0 {
+				err = LPushTaskUnique(c, key, msg, state, ttl)
+			} else {
+				err = LPushTask(c, key, msg, state)
+			}
+			failIfError(err, "Failed to lpush message")
+
+		} else {
+			err := LPushTask(c, key, msg, state)
+			failIfError(err, "Failed to lpush message")
+		}
+	}
+}
+
 // KEYS[1] -> asynq:{<qname>}:t:<task_id>
 // KEYS[2] -> asynq:{<qname>}:scheduled
 // ARGV[1] -> task message data