diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9ee23ed..34b0dae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,7 +14,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `Server` API has changed. Renamed `Quiet` to `Stop`. Renamed `Stop` to `Shutdown`. _Note:_ As a result of this renaming, the behavior of `Stop` has changed. Please update the exising code to call `Shutdown` where it used to call `Stop`.
 - `Scheduler` API has changed. Renamed `Stop` to `Shutdown`.
 - Requires redis v4.0+ for multiple field/value pair support
-- Renamed pending key (TODO: need migration script)
 - `Client.Enqueue` now returns `TaskInfo`
 - `Inspector.RunTaskByKey` is replaced with `Inspector.RunTask`
 - `Inspector.DeleteTaskByKey` is replaced with `Inspector.DeleteTask`
diff --git a/internal/rdb/inspect.go b/internal/rdb/inspect.go
index 31e1fbf..7fcf3f1 100644
--- a/internal/rdb/inspect.go
+++ b/internal/rdb/inspect.go
@@ -994,7 +994,7 @@ else
 	end
 end
 local unique_key = redis.call("HGET", KEYS[1], "unique_key")
-if unique_key ~= nil and unique_key ~= "" and redis.call("GET", unique_key) == ARGV[1] then
+if unique_key and unique_key ~= "" and redis.call("GET", unique_key) == ARGV[1] then
 	redis.call("DEL", unique_key)
 end
 return redis.call("DEL", KEYS[1])
@@ -1094,7 +1094,7 @@ local ids = redis.call("ZRANGE", KEYS[1], 0, -1)
 for _, id in ipairs(ids) do
 	local task_key = ARGV[1] .. id
 	local unique_key = redis.call("HGET", task_key, "unique_key")
-	if unique_key ~= nil and unique_key ~= "" and redis.call("GET", unique_key) == id then
+	if unique_key and unique_key ~= "" and redis.call("GET", unique_key) == id then
 		redis.call("DEL", unique_key)
 	end
 	redis.call("DEL", task_key)
diff --git a/internal/rdb/rdb.go b/internal/rdb/rdb.go
index 36a8343..f65f3c9 100644
--- a/internal/rdb/rdb.go
+++ b/internal/rdb/rdb.go
@@ -32,6 +32,11 @@ func (r *RDB) Close() error {
 	return r.client.Close()
 }
 
+// Client returns the reference to underlying redis client.
+func (r *RDB) Client() redis.UniversalClient {
+	return r.client
+}
+
 // Ping checks the connection with redis server.
 func (r *RDB) Ping() error {
 	return r.client.Ping().Err()
diff --git a/tools/asynq/cmd/migrate.go b/tools/asynq/cmd/migrate.go
new file mode 100644
index 0000000..8ef437d
--- /dev/null
+++ b/tools/asynq/cmd/migrate.go
@@ -0,0 +1,404 @@
+// Copyright 2020 Kentaro Hibino. All rights reserved.
+// Use of this source code is governed by a MIT license
+// that can be found in the LICENSE file.
+
+package cmd
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/go-redis/redis/v7"
+	"github.com/google/uuid"
+	"github.com/hibiken/asynq/internal/base"
+	"github.com/hibiken/asynq/internal/errors"
+	"github.com/hibiken/asynq/internal/rdb"
+	"github.com/spf13/cobra"
+)
+
+// migrateCmd represents the migrate command.
+var migrateCmd = &cobra.Command{
+	Use:   "migrate",
+	Short: fmt.Sprintf("Migrate existing tasks and queues to be asynq%s compatible", base.Version),
+	Long: `Migrate (asynq migrate) will migrate existing tasks and queues in redis to be compatible with the latest version of asynq.
+`,
+	Args: cobra.NoArgs,
+	Run:  migrate,
+}
+
+func init() {
+	rootCmd.AddCommand(migrateCmd)
+}
+
+func backupKey(key string) string {
+	return fmt.Sprintf("%s:backup", key)
+}
+
+func renameKeyAsBackup(c redis.UniversalClient, key string) error {
+	if c.Exists(key).Val() == 0 {
+		return nil // key doesn't exist; no-op
+	}
+	return c.Rename(key, backupKey(key)).Err()
+}
+
+func failIfError(err error, msg string) {
+	if err != nil {
+		fmt.Printf("error: %s: %v\n", msg, err)
+		fmt.Println("*** Please report this issue at https://github.com/hibiken/asynq/issues ***")
+		os.Exit(1)
+	}
+}
+
+func logIfError(err error, msg string) {
+	if err != nil {
+		fmt.Printf("warning: %s: %v\n", msg, err)
+	}
+}
+
+func migrate(cmd *cobra.Command, args []string) {
+	r := createRDB()
+	queues, err := r.AllQueues()
+	failIfError(err, "Failed to get queue names")
+
+	// ---------------------------------------------
+	// Pre-check: Ensure no active servers, tasks.
+	// ---------------------------------------------
+	srvs, err := r.ListServers()
+	failIfError(err, "Failed to get server infos")
+	if len(srvs) > 0 {
+		fmt.Println("(error): Server(s) still running. Please ensure that no asynq servers are running when runnning migrate command.")
+		os.Exit(1)
+	}
+	for _, qname := range queues {
+		stats, err := r.CurrentStats(qname)
+		failIfError(err, "Failed to get stats")
+		if stats.Active > 0 {
+			fmt.Printf("(error): %d active tasks found. Please ensure that no active tasks exist when running migrate command.\n", stats.Active)
+			os.Exit(1)
+		}
+	}
+
+	// ---------------------------------------------
+	// Rename pending key
+	// ---------------------------------------------
+	fmt.Print("Renaming pending keys...")
+	for _, qname := range queues {
+		oldKey := fmt.Sprintf("asynq:{%s}", qname)
+		if r.Client().Exists(oldKey).Val() == 0 {
+			continue
+		}
+		newKey := base.PendingKey(qname)
+		err := r.Client().Rename(oldKey, newKey).Err()
+		failIfError(err, "Failed to rename key")
+	}
+	fmt.Print("Done\n")
+
+	// ---------------------------------------------
+	// Rename keys as backup
+	// ---------------------------------------------
+	fmt.Print("Renaming keys for backup...")
+	for _, qname := range queues {
+		keys := []string{
+			base.ActiveKey(qname),
+			base.PendingKey(qname),
+			base.ScheduledKey(qname),
+			base.RetryKey(qname),
+			base.ArchivedKey(qname),
+		}
+		for _, key := range keys {
+			err := renameKeyAsBackup(r.Client(), key)
+			failIfError(err, fmt.Sprintf("Failed to rename key %q for backup", key))
+		}
+	}
+	fmt.Print("Done\n")
+
+	// ---------------------------------------------
+	// Update to new schema
+	// ---------------------------------------------
+	fmt.Print("Updating to new schema...")
+	for _, qname := range queues {
+		updatePendingMessages(r, qname)
+		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")
+
+	// ---------------------------------------------
+	// Delete backup keys
+	// ---------------------------------------------
+	fmt.Print("Deleting backup keys...")
+	for _, qname := range queues {
+		keys := []string{
+			backupKey(base.ActiveKey(qname)),
+			backupKey(base.PendingKey(qname)),
+			backupKey(base.ScheduledKey(qname)),
+			backupKey(base.RetryKey(qname)),
+			backupKey(base.ArchivedKey(qname)),
+		}
+		for _, key := range keys {
+			err := r.Client().Del(key).Err()
+			failIfError(err, "Failed to delete backup key")
+		}
+	}
+	fmt.Print("Done\n")
+}
+
+func UnmarshalOldMessage(encoded string) (*base.TaskMessage, error) {
+	oldMsg, err := DecodeMessage(encoded)
+	if err != nil {
+		return nil, err
+	}
+	payload, err := json.Marshal(oldMsg.Payload)
+	if err != nil {
+		return nil, fmt.Errorf("could not marshal payload: %v", err)
+	}
+	return &base.TaskMessage{
+		Type:         oldMsg.Type,
+		Payload:      payload,
+		ID:           oldMsg.ID,
+		Queue:        oldMsg.Queue,
+		Retry:        oldMsg.Retry,
+		Retried:      oldMsg.Retried,
+		ErrorMsg:     oldMsg.ErrorMsg,
+		LastFailedAt: 0,
+		Timeout:      oldMsg.Timeout,
+		Deadline:     oldMsg.Deadline,
+		UniqueKey:    oldMsg.UniqueKey,
+	}, nil
+}
+
+// TaskMessage from v0.17
+type OldTaskMessage struct {
+	// Type indicates the kind of the task to be performed.
+	Type string
+
+	// Payload holds data needed to process the task.
+	Payload map[string]interface{}
+
+	// ID is a unique identifier for each task.
+	ID uuid.UUID
+
+	// Queue is a name this message should be enqueued to.
+	Queue string
+
+	// Retry is the max number of retry for this task.
+	Retry int
+
+	// Retried is the number of times we've retried this task so far.
+	Retried int
+
+	// ErrorMsg holds the error message from the last failure.
+	ErrorMsg string
+
+	// Timeout specifies timeout in seconds.
+	// If task processing doesn't complete within the timeout, the task will be retried
+	// if retry count is remaining. Otherwise it will be moved to the archive.
+	//
+	// Use zero to indicate no timeout.
+	Timeout int64
+
+	// Deadline specifies the deadline for the task in Unix time,
+	// the number of seconds elapsed since January 1, 1970 UTC.
+	// If task processing doesn't complete before the deadline, the task will be retried
+	// if retry count is remaining. Otherwise it will be moved to the archive.
+	//
+	// Use zero to indicate no deadline.
+	Deadline int64
+
+	// UniqueKey holds the redis key used for uniqueness lock for this task.
+	//
+	// Empty string indicates that no uniqueness lock was used.
+	UniqueKey string
+}
+
+// DecodeMessage unmarshals the given encoded string and returns a decoded task message.
+// Code from v0.17.
+func DecodeMessage(s string) (*OldTaskMessage, error) {
+	d := json.NewDecoder(strings.NewReader(s))
+	d.UseNumber()
+	var msg OldTaskMessage
+	if err := d.Decode(&msg); err != nil {
+		return nil, err
+	}
+	return &msg, nil
+}
+
+func updatePendingMessages(r *rdb.RDB, qname string) {
+	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 message")
+
+		} else {
+			err := r.Enqueue(msg)
+			failIfError(err, "Failed to enqueue message")
+		}
+	}
+}
+
+// KEYS[1] -> asynq:{<qname>}:t:<task_id>
+// KEYS[2] -> asynq:{<qname>}:scheduled
+// ARGV[1] -> task message data
+// ARGV[2] -> zset score
+// ARGV[3] -> task ID
+// 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 (e.g. "retry", "archived")
+var taskZAddCmd = redis.NewScript(`
+redis.call("HSET", KEYS[1],
+           "msg", ARGV[1],
+           "state", ARGV[6],
+           "timeout", ARGV[4],
+           "deadline", ARGV[5])
+redis.call("ZADD", KEYS[2], ARGV[2], ARGV[3])
+return 1
+`)
+
+// ZAddTask adds task to zset.
+func ZAddTask(c redis.UniversalClient, key string, msg *base.TaskMessage, score float64, state string) error {
+	// Special case; LastFailedAt field is new so assign a value inferred from zscore.
+	if state == "archived" {
+		msg.LastFailedAt = int64(score)
+	}
+
+	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,
+		score,
+		msg.ID.String(),
+		msg.Timeout,
+		msg.Deadline,
+		state,
+	}
+	return taskZAddCmd.Run(c, keys, argv...).Err()
+}
+
+// KEYS[1] -> unique key
+// KEYS[2] -> asynq:{<qname>}:t:<task_id>
+// KEYS[3] -> zset key (e.g. asynq:{<qname>}:scheduled)
+// --
+// ARGV[1] -> task ID
+// ARGV[2] -> uniqueness lock TTL
+// ARGV[3] -> score (process_at timestamp)
+// ARGV[4] -> task message
+// ARGV[5] -> task timeout in seconds (0 if not timeout)
+// ARGV[6] -> task deadline in unix time (0 if no deadline)
+// ARGV[7] -> task state (oneof "scheduled", "retry", "archived")
+var taskZAddUniqueCmd = 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[4],
+           "state", ARGV[7],
+           "timeout", ARGV[5],
+           "deadline", ARGV[6],
+           "unique_key", KEYS[1])
+redis.call("ZADD", KEYS[3], ARGV[3], ARGV[1])
+return 1
+`)
+
+// ScheduleUnique adds the task to the backlog queue to be processed in the future if the uniqueness lock can be acquired.
+// It returns ErrDuplicateTask if the lock cannot be acquired.
+func ZAddTaskUnique(c redis.UniversalClient, key string, msg *base.TaskMessage, score float64, 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()),
+		score,
+		encoded,
+		msg.Timeout,
+		msg.Deadline,
+		state,
+	}
+	res, err := taskZAddUniqueCmd.Run(c, keys, argv...).Result()
+	if err != nil {
+		return err
+	}
+	n, ok := res.(int64)
+	if !ok {
+		return errors.E(errors.Internal, fmt.Sprintf("cast error: unexpected return value from Lua script: %v", res))
+	}
+	if n == 0 {
+		return errors.E(errors.AlreadyExists, errors.ErrDuplicateTask)
+	}
+	return nil
+}
+
+func updateZSetMessages(c redis.UniversalClient, key, state string) {
+	zs, err := c.ZRangeWithScores(backupKey(key), 0, -1).Result()
+	failIfError(err, "Failed to read")
+
+	for _, z := range zs {
+		msg, err := UnmarshalOldMessage(z.Member.(string))
+		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 = ZAddTaskUnique(c, key, msg, z.Score, state, ttl)
+			} else {
+				err = ZAddTask(c, key, msg, z.Score, state)
+			}
+			failIfError(err, "Failed to zadd message")
+		} else {
+			err := ZAddTask(c, key, msg, z.Score, state)
+			failIfError(err, "Failed to enqueue scheduled message")
+		}
+	}
+}
diff --git a/tools/asynq/cmd/root.go b/tools/asynq/cmd/root.go
index 109283f..35fa350 100644
--- a/tools/asynq/cmd/root.go
+++ b/tools/asynq/cmd/root.go
@@ -138,23 +138,24 @@ func createRDB() *rdb.RDB {
 
 // createRDB creates a Inspector instance using flag values and returns it.
 func createInspector() *asynq.Inspector {
-	var connOpt asynq.RedisConnOpt
+	return asynq.NewInspector(getRedisConnOpt())
+}
+
+func getRedisConnOpt() asynq.RedisConnOpt {
 	if useRedisCluster {
 		addrs := strings.Split(viper.GetString("cluster_addrs"), ",")
-		connOpt = asynq.RedisClusterClientOpt{
+		return asynq.RedisClusterClientOpt{
 			Addrs:     addrs,
 			Password:  viper.GetString("password"),
 			TLSConfig: getTLSConfig(),
 		}
-	} else {
-		connOpt = asynq.RedisClientOpt{
-			Addr:      viper.GetString("uri"),
-			DB:        viper.GetInt("db"),
-			Password:  viper.GetString("password"),
-			TLSConfig: getTLSConfig(),
-		}
 	}
-	return asynq.NewInspector(connOpt)
+	return asynq.RedisClientOpt{
+		Addr:      viper.GetString("uri"),
+		DB:        viper.GetInt("db"),
+		Password:  viper.GetString("password"),
+		TLSConfig: getTLSConfig(),
+	}
 }
 
 func getTLSConfig() *tls.Config {
diff --git a/tools/asynq/cmd/stats.go b/tools/asynq/cmd/stats.go
index d569ddb..de83b4c 100644
--- a/tools/asynq/cmd/stats.go
+++ b/tools/asynq/cmd/stats.go
@@ -22,7 +22,7 @@ import (
 var statsCmd = &cobra.Command{
 	Use:   "stats",
 	Short: "Shows current state of the tasks and queues",
-	Long: `Stats (aysnqmon stats) will show the overview of tasks and queues at that instant.
+	Long: `Stats (aysnq stats) will show the overview of tasks and queues at that instant.
 
 Specifically, the command shows the following:
 * Number of tasks in each state