diff --git a/earthquake/explorepolicy/register.go b/earthquake/explorepolicy/register.go
index 9e68121..8ed4cbc 100644
--- a/earthquake/explorepolicy/register.go
+++ b/earthquake/explorepolicy/register.go
@@ -18,9 +18,11 @@ package explorepolicy
 import (
 	dumb "github.com/osrg/earthquake/earthquake/explorepolicy/dumb"
 	random "github.com/osrg/earthquake/earthquake/explorepolicy/random"
+	replayable "github.com/osrg/earthquake/earthquake/explorepolicy/replayable"
 )
 
 func RegisterKnownExplorePolicies() {
 	RegisterPolicy(dumb.Name, func() ExplorePolicy { return dumb.New() })
 	RegisterPolicy(random.Name, func() ExplorePolicy { return random.New() })
+	RegisterPolicy(replayable.Name, func() ExplorePolicy { return replayable.New() })
 }
diff --git a/earthquake/explorepolicy/replayable/replayablepolicy.go b/earthquake/explorepolicy/replayable/replayablepolicy.go
new file mode 100644
index 0000000..ad73e92
--- /dev/null
+++ b/earthquake/explorepolicy/replayable/replayablepolicy.go
@@ -0,0 +1,126 @@
+// Copyright (C) 2015 Nippon Telegraph and Telephone Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+// implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package replayable provides the EXPERIMENTAL semi-deterministic replayable policy.
+package replayable
+
+import (
+	"hash/fnv"
+	"os"
+	"time"
+
+	log "github.com/cihub/seelog"
+	"github.com/osrg/earthquake/earthquake/historystorage"
+	"github.com/osrg/earthquake/earthquake/signal"
+	"github.com/osrg/earthquake/earthquake/util/config"
+)
+
+type Replayable struct {
+	// channel
+	actionCh chan signal.Action
+
+	// parameter "maxInterval"
+	MaxInterval time.Duration
+
+	// parameter "seed"
+	Seed string
+}
+
+func New() *Replayable {
+	log.Warnf("The replayable explorer is EXPERIMENTAL feature.")
+	r := &Replayable{
+		actionCh:    make(chan signal.Action),
+		MaxInterval: time.Duration(0),
+		Seed:        "",
+	}
+	return r
+}
+
+const Name = "replayable"
+
+// returns "replayable"
+func (r *Replayable) Name() string {
+	return Name
+}
+
+// parameters:
+//  - maxInterval(duration): max interval (default: 10 msecs)
+//  - seed(string): seed for replaying (default: empty). can be overriden by EQ_REPLAY_SEED.
+//
+// should support dynamic reloading
+func (r *Replayable) LoadConfig(cfg config.Config) error {
+	log.Debugf("CONFIG: %s", cfg.AllSettings())
+	paramMaxInterval := "explorepolicyparam.maxInterval"
+	if cfg.IsSet(paramMaxInterval) {
+		r.MaxInterval = cfg.GetDuration(paramMaxInterval)
+		log.Infof("Set maxInterval=%s", r.MaxInterval)
+	} else {
+		r.MaxInterval = 10 * time.Millisecond
+		log.Infof("Using default maxInterval=%s", r.MaxInterval)
+	}
+
+	paramSeed := "explorepolicyparam.seed"
+	if cfg.IsSet(paramSeed) {
+		r.Seed = cfg.GetString(paramSeed)
+		log.Infof("Set seed=%s", r.Seed)
+	} else {
+		r.Seed = ""
+		log.Infof("Using default seed=%s", r.Seed)
+	}
+
+	envSeed := "EQ_REPLAY_SEED"
+	if v := os.Getenv(envSeed); v != "" {
+		r.Seed = v
+		log.Infof("Overriding seed=%s (%s)", r.Seed, envSeed)
+	}
+
+	return nil
+}
+
+func (d *Replayable) SetHistoryStorage(storage historystorage.HistoryStorage) error {
+	return nil
+}
+
+func (d *Replayable) ActionChan() chan signal.Action {
+	return d.actionCh
+}
+
+func (r *Replayable) determineInterval(event signal.Event) time.Duration {
+	if r.MaxInterval == 0 {
+		log.Warnf("MaxInterval is zero")
+		return 0
+	}
+	hint := event.ReplayHint()
+	h := fnv.New64a()
+	h.Write([]byte(r.Seed))
+	h.Write([]byte(hint))
+	ui64 := h.Sum64()
+	t := time.Duration(ui64 % uint64(r.MaxInterval))
+	log.Debugf("REPLAYABLE: Determined interval %s for (seed=%s,hint=%s)",
+		t, r.Seed, hint)
+	return t
+}
+
+func (r *Replayable) QueueEvent(event signal.Event) {
+	interval := r.determineInterval(event)
+	action, err := event.DefaultAction()
+	if err != nil {
+		panic(log.Critical(err))
+	}
+	go func() {
+		<-time.After(interval)
+		r.actionCh <- action
+	}()
+}
diff --git a/earthquake/explorepolicy/replayable/replayablepolicy_test.go b/earthquake/explorepolicy/replayable/replayablepolicy_test.go
new file mode 100644
index 0000000..dfd1154
--- /dev/null
+++ b/earthquake/explorepolicy/replayable/replayablepolicy_test.go
@@ -0,0 +1,110 @@
+// Copyright (C) 2015 Nippon Telegraph and Telephone Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+// implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package replayable
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/osrg/earthquake/earthquake/signal"
+	"github.com/osrg/earthquake/earthquake/util/config"
+	logutil "github.com/osrg/earthquake/earthquake/util/log"
+	testutil "github.com/osrg/earthquake/earthquake/util/test"
+)
+
+func TestMain(m *testing.M) {
+	flag.Parse()
+	logutil.InitLog("", true)
+	signal.RegisterKnownSignals()
+	os.Exit(m.Run())
+}
+
+func TestReplayableWithPacketEvent_10_2(t *testing.T) {
+	xTestPolicyWithPacketEvent(t, 10, 2, true)
+}
+
+func TestReplayableWithPacketEvent_10_10(t *testing.T) {
+	xTestPolicyWithPacketEvent(t, 10, 10, true)
+}
+
+func TestReplayableShouldNotBlockWithPacketEvent_10_2(t *testing.T) {
+	xTestPolicyWithPacketEvent(t, 10, 2, false)
+}
+
+func TestReplayableShouldNotBlockWithPacketEvent_10_10(t *testing.T) {
+	xTestPolicyWithPacketEvent(t, 10, 10, false)
+}
+
+func newPolicy(t *testing.T, seed string) *Replayable {
+	policy := New()
+	cfg := config.New()
+	cfg.Set("explorePolicy", "replayable")
+	cfg.Set("explorePolicyParam", map[string]interface{}{
+		"maxInterval": 1 * time.Second,
+		"seed":        seed,
+	})
+	err := policy.LoadConfig(cfg)
+	assert.NoError(t, err)
+	return policy
+}
+
+func xTestPolicyWithPacketEvent(t *testing.T, n, entities int, concurrent bool) {
+	seed := "foobar"
+	policy := newPolicy(t, seed)
+	sender := func() {
+		for i := 0; i < n; i++ {
+			entityID := fmt.Sprintf("entity-%d", i%entities)
+			event := testutil.NewPacketEvent(t, entityID, i).(*signal.PacketEvent)
+			hint := fmt.Sprintf("hint-%s-%d", entityID, i)
+			event.SetReplayHint(hint)
+			t.Logf("Test %d: Sending event (hint=%s)", i, hint)
+			policy.QueueEvent(event)
+			t.Logf("Test %d: Sent event (hint=%s)", i, hint)
+		}
+	}
+	receiver := func() {
+		for i := 0; i < n; i++ {
+			t.Logf("Test %d: Receiving", i)
+			action := <-policy.ActionChan()
+			event := action.Event()
+			t.Logf("Test %d: Received action (event hint=%s)",
+				i, event.ReplayHint())
+		}
+	}
+
+	if concurrent {
+		var wg sync.WaitGroup
+		wg.Add(2)
+		go func() {
+			defer wg.Done()
+			sender()
+		}()
+		go func() {
+			defer wg.Done()
+			receiver()
+		}()
+		wg.Wait()
+	} else {
+		sender()
+		receiver()
+	}
+}
diff --git a/earthquake/signal/event.go b/earthquake/signal/event.go
index 2ec6d06..0178096 100644
--- a/earthquake/signal/event.go
+++ b/earthquake/signal/event.go
@@ -43,6 +43,20 @@ func (this *BasicEvent) SetDeferred(deferred bool) {
 	this.Set("deferred", deferred)
 }
 
+// implements Event
+func (this *BasicEvent) ReplayHint() string {
+	hint, ok := this.Get("replay_hint").(string)
+	if !ok {
+		return ""
+	}
+	return hint
+}
+
+func (this *BasicEvent) SetReplayHint(hint string) {
+	// use BasicSignal.Set() so as to serialize in JSON
+	this.Set("replay_hint", hint)
+}
+
 // implements Event
 func (this *BasicEvent) DefaultAction() (Action, error) {
 	if this.Deferred() {
diff --git a/earthquake/signal/interface.go b/earthquake/signal/interface.go
index 494d8ba..174029e 100644
--- a/earthquake/signal/interface.go
+++ b/earthquake/signal/interface.go
@@ -21,6 +21,15 @@ type Event interface {
 	// json name: "deferred"
 	Deferred() bool
 
+	// explore policy can use this hash string as a hint for semi-deterministic replaying.
+	// The hint should not contain time-dependent or random things for better determinism.
+	// Note that we will not support fully deterministic replaying.
+	//
+	// The hint can contain any character.
+	//
+	// json name: "replay_hint"
+	ReplayHint() string
+
 	// default positive action. can be NopAction, but cannot be nil.
 	// (NopAction is used for history storage)
 	DefaultAction() (Action, error)
diff --git a/example/zk-found-2212.nfqhook/config_replayable_experimental.toml b/example/zk-found-2212.nfqhook/config_replayable_experimental.toml
new file mode 100644
index 0000000..1d9f53a
--- /dev/null
+++ b/example/zk-found-2212.nfqhook/config_replayable_experimental.toml
@@ -0,0 +1,15 @@
+init = "init.sh"
+run = "run.sh"
+validate = "validate.sh"
+clean = "clean.sh"
+restPort = 10080
+
+# The replayable policy enables "semi-deterministic" replaying.
+# You have to specify a "seed" string as EQ_REPLAY_SEED (environmental variable).
+# The replayable policy determines delays as `hash(seed, hint) % maxInterval`.
+# The "hint" is determined by pyearthquake zookeeper inspector.
+explorePolicy = "replayable"
+
+[explorePolicyParam]
+# larger interval can increase reproducibility
+ maxInterval = "100ms"
diff --git a/misc/pyearthquake/inspector/zookeeper.py b/misc/pyearthquake/inspector/zookeeper.py
index 1487787..b26f0df 100644
--- a/misc/pyearthquake/inspector/zookeeper.py
+++ b/misc/pyearthquake/inspector/zookeeper.py
@@ -109,7 +109,9 @@ def map_zktraffic_message_to_event(self, zt_msg):
         src_entity, dst_entity = self.map_zktraffic_message_to_entity_ids(
             zt_msg)
         d = self.map_zktraffic_message_to_dict(zt_msg)
-        event = PacketEvent.from_message(src_entity, dst_entity, d)
+        ## replay_hint is an optional string that helps replaying
+        replay_hint = str(hash(frozenset(d.items())))
+        event = PacketEvent.from_message(src_entity, dst_entity, d, replay_hint)
 
         if isinstance(zt_msg, FLE.Message):
             LOG.debug(colorama.Back.CYAN + colorama.Fore.BLACK +
diff --git a/misc/pyearthquake/signal/event.py b/misc/pyearthquake/signal/event.py
index ccfeaf5..7494f84 100644
--- a/misc/pyearthquake/signal/event.py
+++ b/misc/pyearthquake/signal/event.py
@@ -12,7 +12,7 @@ class PacketEvent(EventBase):
     deferred = True
 
     @classmethod
-    def from_message(cls, src_entity, dst_entity, message):
+    def from_message(cls, src_entity, dst_entity, message, replay_hint=""):
         inst = cls()
         # we do not set inst.entity here
         inst.option = {
@@ -20,6 +20,7 @@ def from_message(cls, src_entity, dst_entity, message):
             'dst_entity': dst_entity,
             'message': message
         }
+        inst.replay_hint = replay_hint
         return inst
 
 
diff --git a/misc/pyearthquake/signal/signal.py b/misc/pyearthquake/signal/signal.py
index 2524969..2482ef2 100644
--- a/misc/pyearthquake/signal/signal.py
+++ b/misc/pyearthquake/signal/signal.py
@@ -101,7 +101,8 @@ class EventBase(SignalBase):
     """
     type_name = 'event'
     deferred = False
-    var_names = SignalBase.var_names + ['deferred']
+    replay_hint = ''
+    var_names = SignalBase.var_names + ['deferred', 'replay_hint']
     # orchestrator sets recv_timestamp
     recv_timestamp = -1