diff --git a/pkg/cron/service.go b/pkg/cron/service.go
index 04775ac42..77a413133 100644
--- a/pkg/cron/service.go
+++ b/pkg/cron/service.go
@@ -65,6 +65,7 @@ type CronService struct {
 	mu        sync.RWMutex
 	running   bool
 	stopChan  chan struct{}
+	wakeChan  chan struct{}
 	gronx     *gronx.Gronx
 }
 
@@ -73,6 +74,7 @@ func NewCronService(storePath string, onJob JobHandler) *CronService {
 		storePath: storePath,
 		onJob:     onJob,
 		gronx:     gronx.New(),
+		wakeChan:  make(chan struct{}),
 	}
 	// Initialize and load store on creation
 	cs.loadStore()
@@ -97,6 +99,9 @@ func (cs *CronService) Start() error {
 	}
 
 	cs.stopChan = make(chan struct{})
+	if cs.wakeChan == nil {
+		cs.wakeChan = make(chan struct{})
+	}
 	cs.running = true
 	go cs.runLoop(cs.stopChan)
 
@@ -119,14 +124,47 @@ func (cs *CronService) Stop() {
 }
 
 func (cs *CronService) runLoop(stopChan chan struct{}) {
-	ticker := time.NewTicker(1 * time.Second)
-	defer ticker.Stop()
+	timer := time.NewTimer(time.Hour)
+	if !timer.Stop() {
+		<-timer.C
+	}
+	defer timer.Stop()
 
 	for {
+		// every loop, recalculate the next wake time
+		cs.mu.RLock()
+		nextWake := cs.getNextWakeMS()
+		cs.mu.RUnlock()
+
+		var delay time.Duration
+		now := time.Now().UnixMilli()
+
+		if nextWake == nil {
+			// no jobs, sleep for a long time (or until a new job is added)
+			delay = time.Hour
+		} else {
+			diff := *nextWake - now
+			if diff <= 0 {
+				delay = 0
+			} else {
+				delay = time.Duration(diff) * time.Millisecond
+			}
+		}
+
+		timer.Reset(delay)
+
 		select {
 		case <-stopChan:
 			return
-		case <-ticker.C:
+		case <-cs.wakeChan: // wake on new job or update
+			if !timer.Stop() {
+				select {
+				case <-timer.C:
+				default:
+				}
+			}
+			continue
+		case <-timer.C:
 			cs.checkJobs()
 		}
 	}
@@ -264,22 +302,19 @@ func (cs *CronService) executeJobByID(jobID string) {
 }
 
 func (cs *CronService) computeNextRun(schedule *CronSchedule, nowMS int64) *int64 {
-	if schedule.Kind == "at" {
+	switch schedule.Kind {
+	case "at":
 		if schedule.AtMS != nil && *schedule.AtMS > nowMS {
 			return schedule.AtMS
 		}
 		return nil
-	}
-
-	if schedule.Kind == "every" {
+	case "every":
 		if schedule.EveryMS == nil || *schedule.EveryMS <= 0 {
 			return nil
 		}
 		next := nowMS + *schedule.EveryMS
 		return &next
-	}
-
-	if schedule.Kind == "cron" {
+	case "cron":
 		if schedule.Expr == "" {
 			return nil
 		}
@@ -294,9 +329,19 @@ func (cs *CronService) computeNextRun(schedule *CronSchedule, nowMS int64) *int6
 
 		nextMS := nextTime.UnixMilli()
 		return &nextMS
+	default:
+		log.Printf("[cron] unknown schedule kind '%s'", schedule.Kind)
+		return nil
 	}
+}
 
-	return nil
+// wake up the loop to re-evaluate next wake time immediately (e.g. after add/update/remove jobs)
+func (cs *CronService) notify() {
+	select {
+	case cs.wakeChan <- struct{}{}:
+	default:
+		// if the channel is full, it means the loop will wake up soon anyway, so we can skip sending
+	}
 }
 
 func (cs *CronService) recomputeNextRuns() {
@@ -400,6 +445,8 @@ func (cs *CronService) AddJob(
 		return nil, err
 	}
 
+	cs.notify()
+
 	return &job, nil
 }
 
@@ -411,6 +458,9 @@ func (cs *CronService) UpdateJob(job *CronJob) error {
 		if cs.store.Jobs[i].ID == job.ID {
 			cs.store.Jobs[i] = *job
 			cs.store.Jobs[i].UpdatedAtMS = time.Now().UnixMilli()
+
+			cs.notify()
+
 			return cs.saveStoreUnsafe()
 		}
 	}
@@ -441,6 +491,8 @@ func (cs *CronService) removeJobUnsafe(jobID string) bool {
 		}
 	}
 
+	cs.notify()
+
 	return removed
 }
 
@@ -463,6 +515,9 @@ func (cs *CronService) EnableJob(jobID string, enabled bool) *CronJob {
 			if err := cs.saveStoreUnsafe(); err != nil {
 				log.Printf("[cron] failed to save store after enable: %v", err)
 			}
+
+			cs.notify()
+
 			return job
 		}
 	}
diff --git a/pkg/cron/service_test.go b/pkg/cron/service_test.go
index 1a0dd1829..c55e62174 100644
--- a/pkg/cron/service_test.go
+++ b/pkg/cron/service_test.go
@@ -1,10 +1,13 @@
 package cron
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 	"runtime"
+	"sync"
 	"testing"
+	"time"
 )
 
 func TestSaveStore_FilePermissions(t *testing.T) {
@@ -36,3 +39,199 @@ func TestSaveStore_FilePermissions(t *testing.T) {
 func int64Ptr(v int64) *int64 {
 	return &v
 }
+
+func setupService(handler JobHandler) (*CronService, string) {
+	tmpFile := fmt.Sprintf("test_cron_%d.json", time.Now().UnixNano())
+	cs := NewCronService(tmpFile, handler)
+	return cs, tmpFile
+}
+
+func TestCronService_CRUD(t *testing.T) {
+	cs, path := setupService(nil)
+	defer os.Remove(path)
+
+	// Test AddJob
+	at := time.Now().Add(time.Hour).UnixMilli()
+	job, err := cs.AddJob("Task1", CronSchedule{Kind: "at", AtMS: &at}, "msg", true, "ch", "to")
+	if err != nil || job.ID == "" {
+		t.Fatalf("AddJob failed: %v", err)
+	}
+
+	// Test ListJobs
+	if len(cs.ListJobs(true)) != 1 {
+		t.Error("ListJobs should return 1 job")
+	}
+
+	// Test UpdateJob
+	job.Name = "UpdatedName"
+	err = cs.UpdateJob(job)
+	if err != nil || cs.store.Jobs[0].Name != "UpdatedName" {
+		t.Error("UpdateJob failed")
+	}
+
+	// Test EnableJob
+	cs.EnableJob(job.ID, false)
+	if cs.store.Jobs[0].Enabled != false || cs.store.Jobs[0].State.NextRunAtMS != nil {
+		t.Error("EnableJob(false) failed to clear state")
+	}
+
+	// Test RemoveJob
+	removed := cs.RemoveJob(job.ID)
+	if !removed || len(cs.store.Jobs) != 0 {
+		t.Error("RemoveJob failed")
+	}
+}
+
+// 2. Test Cron Expression Calculation Logic
+func TestCronService_ComputeNextRun(t *testing.T) {
+	cs, path := setupService(nil)
+	defer os.Remove(path)
+
+	now := time.Date(2024, 1, 1, 12, 0, 0, 0, time.UTC).UnixMilli()
+
+	tests := []struct {
+		name     string
+		schedule CronSchedule
+		wantNil  bool
+	}{
+		{"Valid Cron", CronSchedule{Kind: "cron", Expr: "0 * * * *"}, false},
+		{"Invalid Cron", CronSchedule{Kind: "cron", Expr: "invalid"}, true},
+		{"Every MS", CronSchedule{Kind: "every", EveryMS: int64Ptr(5000)}, false},
+		{"At Future", CronSchedule{Kind: "at", AtMS: int64Ptr(now + 1000)}, false},
+		{"At Past", CronSchedule{Kind: "at", AtMS: int64Ptr(now - 1000)}, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := cs.computeNextRun(&tt.schedule, now)
+			if (got == nil) != tt.wantNil {
+				t.Errorf("%s: got %v, wantNil %v", tt.name, got, tt.wantNil)
+			}
+		})
+	}
+}
+
+// 3. Test Execution Flow
+func TestCronService_ExecutionFlow(t *testing.T) {
+	var mu sync.Mutex
+	executedJobs := make(map[string]bool)
+
+	handler := func(job *CronJob) (string, error) {
+		mu.Lock()
+		executedJobs[job.ID] = true
+		mu.Unlock()
+		return "ok", nil
+	}
+
+	cs, path := setupService(handler)
+	defer os.Remove(path)
+
+	// Start the service
+	if err := cs.Start(); err != nil {
+		t.Fatalf("Start failed: %v", err)
+	}
+	defer cs.Stop()
+
+	// Add a job then runs 100ms from now
+	target := time.Now().Add(100 * time.Millisecond).UnixMilli()
+	job, _ := cs.AddJob("FastJob", CronSchedule{Kind: "at", AtMS: &target}, "", false, "", "")
+
+	// Check for job execution with a timeout
+	success := false
+	for range 20 {
+		mu.Lock()
+		if executedJobs[job.ID] {
+			success = true
+			mu.Unlock()
+			break
+		}
+		mu.Unlock()
+		time.Sleep(100 * time.Millisecond)
+	}
+
+	if !success {
+		t.Error("Job was not executed in time")
+	}
+
+	// check that the job is removed after execution (DeleteAfterRun = true)
+	status := cs.Status()
+	if status["jobs"].(int) != 0 {
+		t.Errorf("Job should be deleted after run, got count: %v", status["jobs"])
+	}
+}
+
+func TestCronService_PersistenceIntegrity(t *testing.T) {
+	tmpFile := "persist_test.json"
+	defer os.Remove(tmpFile)
+
+	// write a job and persist
+	cs1 := NewCronService(tmpFile, nil)
+	at := int64(2000000000000)
+	cs1.AddJob("PersistMe", CronSchedule{Kind: "at", AtMS: &at}, "payload", true, "ch1", "")
+
+	// check file exists
+	if _, err := os.Stat(tmpFile); os.IsNotExist(err) {
+		t.Fatal("Store file was not created")
+	}
+
+	// reload and check data integrity
+	cs2 := NewCronService(tmpFile, nil)
+	if err := cs2.Load(); err != nil {
+		t.Fatalf("Failed to load store: %v", err)
+	}
+
+	jobs := cs2.ListJobs(true)
+	if len(jobs) != 1 || jobs[0].Name != "PersistMe" {
+		t.Errorf("Data corruption after reload. Got: %+v", jobs)
+	}
+
+	// test loading invalid JSON
+	os.WriteFile(tmpFile, []byte("{invalid json}"), 0o644)
+	cs3 := NewCronService(tmpFile, nil)
+	err := cs3.loadStore()
+	if err == nil {
+		t.Error("Should return error when loading invalid JSON")
+	}
+}
+
+func TestCronService_ConcurrentAccess(t *testing.T) {
+	cs, path := setupService(nil)
+	defer os.Remove(path)
+
+	cs.Start()
+	defer cs.Stop()
+
+	var wg sync.WaitGroup
+	workers := 10
+	iterations := 50
+
+	wg.Add(workers * 2)
+
+	// add jobs concurrently
+	for i := range workers {
+		go func(id int) {
+			defer wg.Done()
+			for j := range iterations {
+				at := time.Now().Add(time.Hour).UnixMilli()
+				cs.AddJob(fmt.Sprintf("Job-%d-%d", id, j), CronSchedule{Kind: "at", AtMS: &at}, "", false, "", "")
+				time.Sleep(100 * time.Microsecond)
+			}
+		}(i)
+	}
+
+	// read and update jobs concurrently
+	for range workers {
+		go func() {
+			defer wg.Done()
+			for j := range iterations {
+				jobs := cs.ListJobs(true)
+				if len(jobs) > 0 {
+					cs.EnableJob(jobs[0].ID, j%2 == 0)
+				}
+				time.Sleep(100 * time.Microsecond)
+			}
+		}()
+	}
+
+	wg.Wait()
+}