diff --git a/service/src/main/kotlin/com/sangdol/roomescape/order/business/OrderService.kt b/service/src/main/kotlin/com/sangdol/roomescape/order/business/OrderService.kt
index 1662d322..76a9dcdc 100644
--- a/service/src/main/kotlin/com/sangdol/roomescape/order/business/OrderService.kt
+++ b/service/src/main/kotlin/com/sangdol/roomescape/order/business/OrderService.kt
@@ -36,14 +36,18 @@ class OrderService(
 ) {
 
     fun confirm(reservationId: Long, paymentConfirmRequest: PaymentConfirmRequest) {
-        val trial = paymentAttemptRepository.countByReservationId(reservationId)
+        var trial: Long = 0
         val paymentKey = paymentConfirmRequest.paymentKey
 
         log.info { "[confirm] 결제 및 예약 확정 시작: reservationId=${reservationId}, paymentKey=${paymentKey}" }
-
         try {
-            transactionExecutionUtil.withNewTransaction(isReadOnly = false) {
-                validateAndMarkInProgress(reservationId)
+            trial = transactionExecutionUtil.withNewTransaction(isReadOnly = false) {
+                getTrialAfterValidateCanConfirm(reservationId).also {
+                    reservationService.markInProgress(reservationId)
+                }
+            } ?: run {
+                log.warn { "[confirm] 모든 paymentAttempts 조회 과정에서의 예상치 못한 null 응답: reservationId=${reservationId}" }
+                throw OrderException(OrderErrorCode.BOOKING_UNEXPECTED_ERROR)
             }
 
             val paymentClientResponse: PaymentGatewayResponse =
@@ -61,20 +65,32 @@ class OrderService(
         }
     }
 
-    private fun validateAndMarkInProgress(reservationId: Long) {
+    private fun getTrialAfterValidateCanConfirm(reservationId: Long): Long {
         log.info { "[validateAndMarkInProgress] 예약 확정 가능 여부 검증 시작: reservationId=${reservationId}" }
         val reservation: ReservationStateResponse = reservationService.findStatusWithLock(reservationId)
         val schedule: ScheduleStateResponse = scheduleService.findStateWithLock(reservation.scheduleId)
 
         try {
             orderValidator.validateCanConfirm(reservation, schedule)
-            log.info { "[validateAndMarkInProgress] 예약 확정 가능 여부 검증 완료: reservationId=${reservationId}" }
+
+            return getTrialIfSuccessAttemptNotExists(reservationId).also {
+                log.info { "[validateAndMarkInProgress] 예약 확정 가능 여부 검증 완료: reservationId=${reservationId}" }
+            }
         } catch (e: OrderException) {
             val errorCode = OrderErrorCode.NOT_CONFIRMABLE
             throw OrderException(errorCode, e.message)
         }
+    }
 
-        reservationService.markInProgress(reservationId)
+    private fun getTrialIfSuccessAttemptNotExists(reservationId: Long): Long {
+        val paymentAttempts: List<PaymentAttemptEntity> = paymentAttemptRepository.findAllByReservationId(reservationId)
+
+        if (paymentAttempts.any { it.result == AttemptResult.SUCCESS }) {
+            log.info { "[validateCanConfirm] 이미 결제 완료된 예약: id=${reservationId}" }
+            throw OrderException(OrderErrorCode.BOOKING_ALREADY_COMPLETED)
+        }
+
+        return paymentAttempts.size.toLong()
     }
 
     private fun requestConfirmPayment(
diff --git a/service/src/main/kotlin/com/sangdol/roomescape/order/business/OrderValidator.kt b/service/src/main/kotlin/com/sangdol/roomescape/order/business/OrderValidator.kt
index 8ee18671..7be57c88 100644
--- a/service/src/main/kotlin/com/sangdol/roomescape/order/business/OrderValidator.kt
+++ b/service/src/main/kotlin/com/sangdol/roomescape/order/business/OrderValidator.kt
@@ -16,18 +16,11 @@ import java.time.LocalDateTime
 private val log: KLogger = KotlinLogging.logger {}
 
 @Component
-class OrderValidator(
-    private val paymentAttemptRepository: PaymentAttemptRepository
-) {
+class OrderValidator {
     fun validateCanConfirm(
         reservation: ReservationStateResponse,
         schedule: ScheduleStateResponse
     ) {
-        if (paymentAttemptRepository.isSuccessAttemptExists(reservation.id)) {
-            log.info { "[validateCanConfirm] 이미 결제 완료된 예약: id=${reservation.id}" }
-            throw OrderException(OrderErrorCode.BOOKING_ALREADY_COMPLETED)
-        }
-
         validateReservationStatus(reservation)
         validateScheduleStatus(schedule)
     }
diff --git a/service/src/main/kotlin/com/sangdol/roomescape/order/infrastructure/persistence/PaymentAttemptRepository.kt b/service/src/main/kotlin/com/sangdol/roomescape/order/infrastructure/persistence/PaymentAttemptRepository.kt
index 3c5e8666..4f2ff58f 100644
--- a/service/src/main/kotlin/com/sangdol/roomescape/order/infrastructure/persistence/PaymentAttemptRepository.kt
+++ b/service/src/main/kotlin/com/sangdol/roomescape/order/infrastructure/persistence/PaymentAttemptRepository.kt
@@ -23,4 +23,6 @@ interface PaymentAttemptRepository: JpaRepository<PaymentAttemptEntity, Long> {
     """
     )
     fun isSuccessAttemptExists(reservationId: Long): Boolean
+
+    fun findAllByReservationId(reservationId: Long): List<PaymentAttemptEntity>
 }
diff --git a/service/src/test/kotlin/com/sangdol/roomescape/order/OrderConcurrencyTest.kt b/service/src/test/kotlin/com/sangdol/roomescape/order/OrderConcurrencyTest.kt
index 54519080..768323d7 100644
--- a/service/src/test/kotlin/com/sangdol/roomescape/order/OrderConcurrencyTest.kt
+++ b/service/src/test/kotlin/com/sangdol/roomescape/order/OrderConcurrencyTest.kt
@@ -108,6 +108,8 @@ class OrderConcurrencyTest(
                     }
                 }
 
+                delay(10)
+
                 async {
                     assertThrows<OrderException> {
                         orderService.confirm(reservation.id, paymentConfirmRequest)
diff --git a/test-scripts/common.js b/test-scripts/common.js
index 0816cb4a..3f3e6098 100644
--- a/test-scripts/common.js
+++ b/test-scripts/common.js
@@ -32,7 +32,7 @@ export function maxIterations() {
 
 export function fetchUsers() {
     const userCount = Math.round(maxIterations() * 0.5)
-    const userAccountRes = http.get(`${BASE_URL}/tests/users?count=${userCount}`)
+    const userAccountRes = http.get(`http://localhost:8080/tests/users?count=${userCount}`)
 
     if (userAccountRes.status !== 200) {
         throw new Error('users 조회 실패')
@@ -42,7 +42,7 @@ export function fetchUsers() {
 }
 
 export function fetchStores() {
-    const storeIdListRes = http.get(`${BASE_URL}/tests/stores`)
+    const storeIdListRes = http.get(`http://localhost:8080/tests/stores`)
 
     if (storeIdListRes.status !== 200) {
         throw new Error('stores 조회 실패')
diff --git a/test-scripts/create-reservation-scripts.js b/test-scripts/create-reservation-scripts.js
index 4f33b6c1..d5c26aca 100644
--- a/test-scripts/create-reservation-scripts.js
+++ b/test-scripts/create-reservation-scripts.js
@@ -15,19 +15,10 @@ export const options = {
     scenarios: {
         user_reservation: {
             executor: 'ramping-vus',
-            startVUs: 0,
+            startVUs: 1500,
             stages: [
-                { duration: '1m', target: 100 },
-                { duration: '1m', target: 200 },
-                { duration: '1m', target: 300 },
-                { duration: '1m', target: 300 },
-                { duration: '1m', target: 400 },
-                { duration: '1m', target: 500 },
-                { duration: '2m', target: 500 },
-                { duration: '1m', target: 600 },
-                { duration: '1m', target: 800 },
-                { duration: '1m', target: 1000 },
-                { duration: '3m', target: 0 },
+                { duration: '10m', target: 1500 },
+                { duration: '1m', target: 0 }
             ]
         }
     },
@@ -84,13 +75,13 @@ export default function (data) {
 
     const user = randomItem(users)
     const accessToken = login(user.account, user.password, 'USER').accessToken
-    const storeId = randomItem(stores).storeId
+    let storeId = randomItem(stores).storeId
 
     if (!accessToken) {
         console.log(`로그인 실패: token=${accessToken}`)
         return
     }
-    const targetDate = randomDayBetween(1, 4)
+    let targetDate
 
     let availableScheduleId, selectedThemeId, selectedThemeInfo, reservationId, totalAmount
 
@@ -99,6 +90,8 @@ export default function (data) {
         let schedules
 
         while (searchTrial < 5) {
+            storeId = randomItem(stores).storeId
+            targetDate = randomDayBetween(1, 7)
             const res = http.get(`${BASE_URL}/stores/${storeId}/schedules?date=${targetDate}`)
             const result = check(res, {'일정 조회 성공': (r) => r.status === 200})
             if (result !== true) {
@@ -145,7 +138,7 @@ export default function (data) {
     let isScheduleHeld = false
     group(`일정 Holding 및 테마 정보 조회 -> 예약 과정중 첫 페이지의 작업 완료`, function () {
         const holdRes = http.post(`${BASE_URL}/schedules/${availableScheduleId}/hold`, null, getHeaders(accessToken))
-        const body = JSON.parse(holdRes)
+        const body = JSON.parse(holdRes.body)
 
         if (check(holdRes, {'일정 점유 성공': (r) => r.status === 200})) {
             const themeInfoRes = http.get(`${BASE_URL}/themes/${selectedThemeId}`)
diff --git a/test-scripts/create-schedule-scripts.js b/test-scripts/create-schedule-scripts.js
index 9d533cf3..35eb6a39 100644
--- a/test-scripts/create-schedule-scripts.js
+++ b/test-scripts/create-schedule-scripts.js
@@ -13,7 +13,7 @@ export const options = {
             executor: 'shared-iterations',
             vus: 263,
             iterations: TOTAL_ITERATIONS,
-            maxDuration: '10m',
+            maxDuration: '30m',
         },
     },
     thresholds: {
@@ -113,7 +113,7 @@ function createSchedule(storeId, accessToken, schedule) {
 function generateDates(days) {
     const dates = [];
     const today = new Date();
-    for (let i = 1; i < days; i++) {
+    for (let i = 1; i <= days; i++) {
         const date = new Date(today);
         date.setDate(today.getDate() + i);
         dates.push(date.toISOString().split('T')[0]);