diff --git a/apps/backend/apps/client/src/assignment/assignment.controller.ts b/apps/backend/apps/client/src/assignment/assignment.controller.ts
index 90a9463b1..47be75910 100644
--- a/apps/backend/apps/client/src/assignment/assignment.controller.ts
+++ b/apps/backend/apps/client/src/assignment/assignment.controller.ts
@@ -1,27 +1,18 @@
 import {
   Controller,
-  InternalServerErrorException,
-  NotFoundException,
   Param,
   Post,
   Req,
   Get,
   Query,
-  Logger,
   DefaultValuePipe,
   Delete
 } from '@nestjs/common'
-import { Prisma } from '@prisma/client'
 import {
   AuthNotNeededIfOpenSpace,
   AuthenticatedRequest,
   UserNullWhenAuthFailedIfOpenSpace
 } from '@libs/auth'
-import {
-  ConflictFoundException,
-  EntityNotExistException,
-  ForbiddenAccessException
-} from '@libs/exception'
 import {
   CursorValidationPipe,
   GroupIDPipe,
@@ -32,8 +23,6 @@ import { AssignmentService } from './assignment.service'
 
 @Controller('assignment')
 export class AssignmentController {
-  private readonly logger = new Logger(AssignmentController.name)
-
   constructor(private readonly assignmentService: AssignmentService) {}
 
   @Get('ongoing-upcoming')
@@ -41,12 +30,7 @@ export class AssignmentController {
   async getOngoingUpcomingAssignments(
     @Query('groupId', GroupIDPipe) groupId: number
   ) {
-    try {
-      return await this.assignmentService.getAssignmentsByGroupId(groupId)
-    } catch (error) {
-      this.logger.error(error)
-      throw new InternalServerErrorException()
-    }
+    return await this.assignmentService.getAssignmentsByGroupId(groupId)
   }
 
   @Get('ongoing-upcoming-with-registered')
@@ -54,15 +38,10 @@ export class AssignmentController {
     @Req() req: AuthenticatedRequest,
     @Query('groupId', GroupIDPipe) groupId: number
   ) {
-    try {
-      return await this.assignmentService.getAssignmentsByGroupId(
-        groupId,
-        req.user.id
-      )
-    } catch (error) {
-      this.logger.error(error)
-      throw new InternalServerErrorException()
-    }
+    return await this.assignmentService.getAssignmentsByGroupId(
+      groupId,
+      req.user.id
+    )
   }
 
   @Get('finished')
@@ -75,18 +54,13 @@ export class AssignmentController {
     take: number,
     @Query('search') search?: string
   ) {
-    try {
-      return await this.assignmentService.getFinishedAssignmentsByGroupId(
-        req.user?.id,
-        cursor,
-        take,
-        groupId,
-        search
-      )
-    } catch (error) {
-      this.logger.error(error)
-      throw new InternalServerErrorException()
-    }
+    return await this.assignmentService.getFinishedAssignmentsByGroupId(
+      req.user?.id,
+      cursor,
+      take,
+      groupId,
+      search
+    )
   }
 
   @Get('registered-finished')
@@ -98,18 +72,13 @@ export class AssignmentController {
     take: number,
     @Query('search') search?: string
   ) {
-    try {
-      return await this.assignmentService.getRegisteredFinishedAssignments(
-        cursor,
-        take,
-        groupId,
-        req.user.id,
-        search
-      )
-    } catch (error) {
-      this.logger.error(error)
-      throw new InternalServerErrorException()
-    }
+    return await this.assignmentService.getRegisteredFinishedAssignments(
+      cursor,
+      take,
+      groupId,
+      req.user.id,
+      search
+    )
   }
 
   @Get('registered-ongoing-upcoming')
@@ -118,16 +87,11 @@ export class AssignmentController {
     @Query('groupId', GroupIDPipe) groupId: number,
     @Query('search') search?: string
   ) {
-    try {
-      return await this.assignmentService.getRegisteredOngoingUpcomingAssignments(
-        groupId,
-        req.user.id,
-        search
-      )
-    } catch (error) {
-      this.logger.error(error)
-      throw new InternalServerErrorException()
-    }
+    return await this.assignmentService.getRegisteredOngoingUpcomingAssignments(
+      groupId,
+      req.user.id,
+      search
+    )
   }
 
   @Get(':id')
@@ -137,19 +101,7 @@ export class AssignmentController {
     @Query('groupId', GroupIDPipe) groupId: number,
     @Param('id', new RequiredIntPipe('id')) id: number
   ) {
-    try {
-      return await this.assignmentService.getAssignment(
-        id,
-        groupId,
-        req.user?.id
-      )
-    } catch (error) {
-      if (error instanceof EntityNotExistException) {
-        throw error.convert2HTTPException()
-      }
-      this.logger.error(error)
-      throw new InternalServerErrorException()
-    }
+    return await this.assignmentService.getAssignment(id, groupId, req.user?.id)
   }
 
   @Post(':id/participation')
@@ -159,25 +111,12 @@ export class AssignmentController {
     @Param('id', IDValidationPipe) assignmentId: number,
     @Query('invitationCode') invitationCode?: string
   ) {
-    try {
-      return await this.assignmentService.createAssignmentRecord(
-        assignmentId,
-        req.user.id,
-        invitationCode,
-        groupId
-      )
-    } catch (error) {
-      if (
-        error instanceof Prisma.PrismaClientKnownRequestError &&
-        error.name === 'NotFoundError'
-      ) {
-        throw new NotFoundException(error.message)
-      } else if (error instanceof ConflictFoundException) {
-        throw error.convert2HTTPException()
-      }
-      this.logger.error(error)
-      throw new InternalServerErrorException(error.message)
-    }
+    return await this.assignmentService.createAssignmentRecord(
+      assignmentId,
+      req.user.id,
+      invitationCode,
+      groupId
+    )
   }
 
   // unregister only for upcoming Assignment
@@ -187,21 +126,10 @@ export class AssignmentController {
     @Query('groupId', GroupIDPipe) groupId: number,
     @Param('id', IDValidationPipe) assignmentId: number
   ) {
-    try {
-      return await this.assignmentService.deleteAssignmentRecord(
-        assignmentId,
-        req.user.id,
-        groupId
-      )
-    } catch (error) {
-      if (
-        error instanceof ForbiddenAccessException ||
-        error instanceof EntityNotExistException
-      ) {
-        throw error.convert2HTTPException()
-      }
-      this.logger.error(error)
-      throw new InternalServerErrorException(error.message)
-    }
+    return await this.assignmentService.deleteAssignmentRecord(
+      assignmentId,
+      req.user.id,
+      groupId
+    )
   }
 }
diff --git a/apps/backend/apps/client/src/assignment/assignment.service.ts b/apps/backend/apps/client/src/assignment/assignment.service.ts
index 1d3ba116f..52aac2b29 100644
--- a/apps/backend/apps/client/src/assignment/assignment.service.ts
+++ b/apps/backend/apps/client/src/assignment/assignment.service.ts
@@ -467,31 +467,23 @@ export class AssignmentService {
     userId: number,
     groupId = OPEN_SPACE_ID
   ) {
-    let assignment
-    try {
-      assignment = await this.prisma.assignment.findUniqueOrThrow({
+    const [assignment, assignmentRecord] = await Promise.all([
+      this.prisma.contest.findUnique({
         where: { id: assignmentId, groupId }
-      })
-    } catch (err) {
-      if (
-        err instanceof Prisma.PrismaClientKnownRequestError &&
-        err.code === 'P2025'
-      ) {
-        throw new EntityNotExistException('Assignment')
-      }
-    }
-    try {
-      await this.prisma.assignmentRecord.findFirstOrThrow({
+      }),
+      this.prisma.assignmentRecord.findFirst({
         where: { userId, assignmentId }
       })
-    } catch (err) {
-      if (
-        err instanceof Prisma.PrismaClientKnownRequestError &&
-        err.code === 'P2025'
-      ) {
-        throw new EntityNotExistException('AssignmentRecord')
-      }
+    ])
+
+    if (!assignment) {
+      throw new EntityNotExistException('Contest')
+    }
+
+    if (!assignmentRecord) {
+      throw new EntityNotExistException('ContestRecord')
     }
+
     const now = new Date()
     if (now >= assignment.startTime) {
       throw new ForbiddenAccessException(
@@ -499,18 +491,9 @@ export class AssignmentService {
       )
     }
 
-    try {
-      return await this.prisma.assignmentRecord.delete({
-        // eslint-disable-next-line @typescript-eslint/naming-convention
-        where: { assignmentId_userId: { assignmentId, userId } }
-      })
-    } catch (err) {
-      if (
-        err instanceof Prisma.PrismaClientKnownRequestError &&
-        err.code === 'P2025'
-      ) {
-        throw new EntityNotExistException('AssignmentRecord')
-      }
-    }
+    return await this.prisma.assignmentRecord.delete({
+      // eslint-disable-next-line @typescript-eslint/naming-convention
+      where: { assignmentId_userId: { assignmentId, userId } }
+    })
   }
 }