diff --git a/di/wire_gen.go b/di/wire_gen.go
index d09b64f..bc5816a 100644
--- a/di/wire_gen.go
+++ b/di/wire_gen.go
@@ -50,7 +50,7 @@ func Init() (Container, error) {
 	authService := auth.NewService(authRepository, zapLogger, config)
 	authHandler := auth.NewHandler(authService, zapLogger)
 	evtregRepository := evtreg.NewRepository(db)
-	evtregService := evtreg.NewService(zapLogger, evtregRepository)
+	evtregService := evtreg.NewService(zapLogger, evtregRepository, eventCache)
 	evtregHandler := evtreg.NewHandler(evtregService)
 	corsHandler := cfgldr.MakeCorsConfig(config)
 	authMiddleware := middleware.NewAuthMiddleware(authRepository, config)
diff --git a/internal/event/event.cache.go b/internal/event/event.cache.go
index 2d938d2..02a00c1 100644
--- a/internal/event/event.cache.go
+++ b/internal/event/event.cache.go
@@ -13,6 +13,7 @@ import (
 type Cache interface {
 	Get(ctx context.Context, key string) (bool, string, *apperror.AppError)
 	Set(ctx context.Context, key string, value string, expiration time.Duration) *apperror.AppError
+	Del(ctx context.Context, keys ...string) *apperror.AppError
 }
 
 type cacheImpl struct {
@@ -48,3 +49,11 @@ func (s *cacheImpl) Set(ctx context.Context, key string, value string, expiratio
 		return nil
 	}
 }
+
+func (s *cacheImpl) Del(ctx context.Context, keys ...string) *apperror.AppError {
+	if err := s.redis.Del(ctx, keys...).Err(); err != nil {
+		s.logger.Error("could not delete keys", zap.Strings("keys", keys), zap.Error(err))
+		return apperror.InternalError
+	}
+	return nil
+}
diff --git a/internal/event/event.handler.go b/internal/event/event.handler.go
index d1dd594..f34670d 100644
--- a/internal/event/event.handler.go
+++ b/internal/event/event.handler.go
@@ -133,5 +133,5 @@ func (h *handlerImpl) GetEventById(c *gin.Context) {
 
 func setHeader(c *gin.Context) {
 	c.Header("Content-Type", "application/json; charset=utf-8")
-	c.Header("Cache-Control", "public, max-age=3600")
+	c.Header("Cache-Control", "public, max-age=30")
 }
diff --git a/internal/evtreg/evtreg.handler.go b/internal/evtreg/evtreg.handler.go
index e42e99b..b732c9f 100644
--- a/internal/evtreg/evtreg.handler.go
+++ b/internal/evtreg/evtreg.handler.go
@@ -48,8 +48,9 @@ func (h *handlerImpl) RegisterEvent(c *gin.Context) {
 		return
 	}
 
-	if apperr := h.svc.RegisterEvent(email, scheduleId); apperr != nil {
+	if apperr := h.svc.RegisterEvent(c, email, scheduleId); apperr != nil {
 		utils.ReturnError(c, apperr)
+		return
 	}
 
 	c.AbortWithStatus(http.StatusNoContent)
diff --git a/internal/evtreg/evtreg.repository.go b/internal/evtreg/evtreg.repository.go
index 7611be8..76e494b 100644
--- a/internal/evtreg/evtreg.repository.go
+++ b/internal/evtreg/evtreg.repository.go
@@ -24,11 +24,11 @@ type repositoryImpl struct {
 }
 
 func (r *repositoryImpl) GetUserWithEventRegistrationByEmail(user *model.User, email string) error {
-	return r.db.Preload("RegisteredEvents").Preload("RegisteredEvents.Schedule").Where("email = ?", email).First(&user).Error
+	return r.db.Model(user).Preload("RegisteredEvents").Preload("RegisteredEvents.Schedule").Where("email = ?", email).First(&user).Error
 }
 
 func (r *repositoryImpl) GetScheduleById(schedule *model.Schedule, scheduleId int) error {
-	return r.db.Where("id = ?", scheduleId).First(schedule).Error
+	return r.db.Model(schedule).Where("id = ?", scheduleId).First(schedule).Error
 }
 
 func (r *repositoryImpl) RegisterEvent(userId int, scheduleId int) error {
diff --git a/internal/evtreg/evtreg.service.go b/internal/evtreg/evtreg.service.go
index 09d4a11..83913a5 100644
--- a/internal/evtreg/evtreg.service.go
+++ b/internal/evtreg/evtreg.service.go
@@ -1,22 +1,26 @@
 package evtreg
 
 import (
+	"context"
 	"errors"
+	"fmt"
 
 	"github.com/isd-sgcu/oph66-backend/apperror"
+	"github.com/isd-sgcu/oph66-backend/internal/event"
 	"github.com/isd-sgcu/oph66-backend/internal/model"
 	"go.uber.org/zap"
 	"gorm.io/gorm"
 )
 
 type Service interface {
-	RegisterEvent(userEmail string, scheduleId int) *apperror.AppError
+	RegisterEvent(ctx context.Context, userEmail string, scheduleId int) *apperror.AppError
 }
 
-func NewService(logger *zap.Logger, repo Repository) Service {
+func NewService(logger *zap.Logger, repo Repository, cache event.Cache) Service {
 	return &serviceImpl{
 		logger,
 		repo,
+		cache,
 	}
 }
 
@@ -25,9 +29,10 @@ var _ Service = &serviceImpl{}
 type serviceImpl struct {
 	logger *zap.Logger
 	repo   Repository
+	cache  event.Cache
 }
 
-func (h *serviceImpl) RegisterEvent(userEmail string, scheduleId int) *apperror.AppError {
+func (h *serviceImpl) RegisterEvent(ctx context.Context, userEmail string, scheduleId int) *apperror.AppError {
 	var user model.User
 	if err := h.repo.GetUserWithEventRegistrationByEmail(&user, userEmail); errors.Is(err, gorm.ErrRecordNotFound) {
 		return apperror.UserNotFound
@@ -57,5 +62,10 @@ func (h *serviceImpl) RegisterEvent(userEmail string, scheduleId int) *apperror.
 		return apperror.InternalError
 	}
 
+	keys := []string{fmt.Sprintf("get_event_by_id-%v", schedule.EventId), "get_all_events"}
+	if apperr := h.cache.Del(ctx, keys...); apperr != nil {
+		return apperr
+	}
+
 	return nil
 }
diff --git a/migrations/00-init.sql b/migrations/00-init.sql
index a32b7c7..0d3dd9c 100644
--- a/migrations/00-init.sql
+++ b/migrations/00-init.sql
@@ -134,3 +134,17 @@ CREATE TABLE event_registrations (
 );
 
 INSERT INTO feature_flags(key, enabled, cache_duration, extra_info) VALUES ('livestream', FALSE, 10, '{"url": "https://www.youtube.com/watch?v=0tOXxuLcaog"}');
+
+CREATE OR REPLACE FUNCTION update_attandee_count()
+ RETURNS void
+ LANGUAGE plpgsql
+AS $function$
+declare
+	sid INTEGER;
+	cnt INTEGER;
+BEGIN
+for sid, cnt in select id, count(user_id) from schedules s left join event_registrations er on s.id = er.schedule_id group by s.id loop
+	update schedules set current_attendee = cnt where id = sid;
+end loop;
+end;
+$function$;