SPMS.Application/DTOs/Device/DeviceAgreeRequestDto.cs

@@ -7,7 +7,7 @@ public class DeviceAgreeRequestDto
 {
     [Required]
     [JsonPropertyName("device_id")]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 
     [Required]
     [JsonPropertyName("push_agreed")]

SPMS.Application/DTOs/Device/DeviceDeleteRequestDto.cs

@@ -7,5 +7,5 @@ public class DeviceDeleteRequestDto
 {
     [Required]
     [JsonPropertyName("device_id")]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 }

SPMS.Application/DTOs/Device/DeviceInfoRequestDto.cs

@@ -7,5 +7,5 @@ public class DeviceInfoRequestDto
 {
     [Required]
     [JsonPropertyName("device_id")]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 }

SPMS.Application/DTOs/Device/DeviceInfoResponseDto.cs

@@ -5,7 +5,7 @@ namespace SPMS.Application.DTOs.Device;
 public class DeviceInfoResponseDto
 {
     [JsonPropertyName("device_id")]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 
     [JsonPropertyName("device_token")]
     public string DeviceToken { get; set; } = string.Empty;

SPMS.Application/DTOs/Device/DeviceListResponseDto.cs

@@ -15,7 +15,7 @@ public class DeviceListResponseDto
 public class DeviceSummaryDto
 {
     [JsonPropertyName("device_id")]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 
     [JsonPropertyName("platform")]
     public string Platform { get; set; } = string.Empty;

SPMS.Application/DTOs/Device/DeviceRegisterRequestDto.cs

@@ -5,6 +5,10 @@ namespace SPMS.Application.DTOs.Device;
 
 public class DeviceRegisterRequestDto
 {
+    [Required]
+    [JsonPropertyName("device_id")]
+    public string DeviceId { get; set; } = string.Empty;
+
     [Required]
     [JsonPropertyName("device_token")]
     public string DeviceToken { get; set; } = string.Empty;

SPMS.Application/DTOs/Device/DeviceRegisterResponseDto.cs

@@ -5,7 +5,7 @@ namespace SPMS.Application.DTOs.Device;
 public class DeviceRegisterResponseDto
 {
     [JsonPropertyName("device_id")]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 
     [JsonPropertyName("is_new")]
     public bool IsNew { get; set; }

SPMS.Application/DTOs/Device/DeviceTagsRequestDto.cs

@@ -7,7 +7,7 @@ public class DeviceTagsRequestDto
 {
     [Required]
     [JsonPropertyName("device_id")]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 
     [Required]
     [JsonPropertyName("tags")]

SPMS.Application/DTOs/Device/DeviceUpdateRequestDto.cs

@@ -7,7 +7,7 @@ public class DeviceUpdateRequestDto
 {
     [Required]
     [JsonPropertyName("device_id")]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 
     [JsonPropertyName("device_token")]
     public string? DeviceToken { get; set; }

SPMS.Application/DTOs/Push/PushLogResponseDto.cs

@@ -21,7 +21,7 @@ public class PushLogItemDto
     public string MessageCode { get; set; } = string.Empty;
 
     [JsonPropertyName("device_id")]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 
     [JsonPropertyName("status")]
     public string Status { get; set; } = string.Empty;

SPMS.Application/DTOs/Push/PushScheduleRequestDto.cs

@@ -10,7 +10,7 @@ public class PushScheduleRequestDto
     [Required]
     public string SendType { get; set; } = string.Empty;
 
-    public long? DeviceId { get; set; }
+    public string? DeviceId { get; set; }
 
     public List<string>? Tags { get; set; }
 

SPMS.Application/DTOs/Push/PushSendRequestDto.cs

@@ -8,7 +8,7 @@ public class PushSendRequestDto
     public string MessageCode { get; set; } = string.Empty;
 
     [Required]
-    public long DeviceId { get; set; }
+    public string DeviceId { get; set; } = string.Empty;
 
     public Dictionary<string, string>? Variables { get; set; }
 }

SPMS.Application/Interfaces/IDeviceService.cs

@@ -8,7 +8,7 @@ public interface IDeviceService
     Task<DeviceInfoResponseDto> GetInfoAsync(long serviceId, DeviceInfoRequestDto request);
     Task UpdateAsync(long serviceId, DeviceUpdateRequestDto request);
     Task DeleteAsync(long serviceId, DeviceDeleteRequestDto request);
-    Task AdminDeleteAsync(long deviceId);
+    Task AdminDeleteAsync(string externalDeviceId);
     Task<DeviceListResponseDto> GetListAsync(long? serviceId, DeviceListRequestDto request);
     Task<byte[]> ExportAsync(long? serviceId, DeviceExportRequestDto request);
     Task SetTagsAsync(long serviceId, DeviceTagsRequestDto request);

SPMS.Application/Interfaces/ITokenCacheService.cs

@@ -2,9 +2,9 @@ namespace SPMS.Application.Interfaces;
 
 public interface ITokenCacheService
 {
-    Task<CachedDeviceInfo?> GetDeviceInfoAsync(long serviceId, long deviceId);
+    Task<CachedDeviceInfo?> GetDeviceInfoAsync(long serviceId, string deviceId);
-    Task SetDeviceInfoAsync(long serviceId, long deviceId, CachedDeviceInfo info);
+    Task SetDeviceInfoAsync(long serviceId, string deviceId, CachedDeviceInfo info);
-    Task InvalidateAsync(long serviceId, long deviceId);
+    Task InvalidateAsync(long serviceId, string deviceId);
     Task InvalidateByServiceAsync(long serviceId);
 }
 

SPMS.Application/Services/DeviceService.cs

@@ -35,6 +35,7 @@ public class DeviceService : IDeviceService
 
         if (existing != null)
         {
+            existing.ExternalDeviceId = request.DeviceId;
             existing.Platform = platform;
             existing.OsVersion = request.OsVersion;
             existing.AppVersion = request.AppVersion;
@@ -43,14 +44,15 @@ public class DeviceService : IDeviceService
             existing.UpdatedAt = DateTime.UtcNow;
             _deviceRepository.Update(existing);
             await _unitOfWork.SaveChangesAsync();
-            await _tokenCache.InvalidateAsync(serviceId, existing.Id);
+            await _tokenCache.InvalidateAsync(serviceId, existing.ExternalDeviceId);
 
-            return new DeviceRegisterResponseDto { DeviceId = existing.Id, IsNew = false };
+            return new DeviceRegisterResponseDto { DeviceId = existing.ExternalDeviceId, IsNew = false };
         }
 
         var device = new Device
         {
             ServiceId = serviceId,
+            ExternalDeviceId = request.DeviceId,
             DeviceToken = request.DeviceToken,
             Platform = platform,
             OsVersion = request.OsVersion,
@@ -64,18 +66,18 @@ public class DeviceService : IDeviceService
 
         await _deviceRepository.AddAsync(device);
         await _unitOfWork.SaveChangesAsync();
-        return new DeviceRegisterResponseDto { DeviceId = device.Id, IsNew = true };
+        return new DeviceRegisterResponseDto { DeviceId = device.ExternalDeviceId, IsNew = true };
     }
 
     public async Task<DeviceInfoResponseDto> GetInfoAsync(long serviceId, DeviceInfoRequestDto request)
     {
-        var device = await _deviceRepository.GetByIdAndServiceAsync(request.DeviceId, serviceId);
+        var device = await _deviceRepository.GetByExternalIdAndServiceAsync(request.DeviceId, serviceId);
         if (device == null)
             throw new SpmsException(ErrorCodes.DeviceNotFound, "존재하지 않는 디바이스입니다.", 404);
 
         return new DeviceInfoResponseDto
         {
-            DeviceId = device.Id,
+            DeviceId = device.ExternalDeviceId,
             DeviceToken = device.DeviceToken,
             Platform = device.Platform.ToString().ToLowerInvariant(),
             OsVersion = device.OsVersion,
@@ -92,7 +94,7 @@ public class DeviceService : IDeviceService
 
     public async Task UpdateAsync(long serviceId, DeviceUpdateRequestDto request)
     {
-        var device = await _deviceRepository.GetByIdAndServiceAsync(request.DeviceId, serviceId);
+        var device = await _deviceRepository.GetByExternalIdAndServiceAsync(request.DeviceId, serviceId);
         if (device == null)
             throw new SpmsException(ErrorCodes.DeviceNotFound, "존재하지 않는 디바이스입니다.", 404);
 
@@ -106,12 +108,12 @@ public class DeviceService : IDeviceService
         device.UpdatedAt = DateTime.UtcNow;
         _deviceRepository.Update(device);
         await _unitOfWork.SaveChangesAsync();
-        await _tokenCache.InvalidateAsync(serviceId, device.Id);
+        await _tokenCache.InvalidateAsync(serviceId, device.ExternalDeviceId);
     }
 
     public async Task DeleteAsync(long serviceId, DeviceDeleteRequestDto request)
     {
-        var device = await _deviceRepository.GetByIdAndServiceAsync(request.DeviceId, serviceId);
+        var device = await _deviceRepository.GetByExternalIdAndServiceAsync(request.DeviceId, serviceId);
         if (device == null)
             throw new SpmsException(ErrorCodes.DeviceNotFound, "존재하지 않는 디바이스입니다.", 404);
 
@@ -119,12 +121,13 @@ public class DeviceService : IDeviceService
         device.UpdatedAt = DateTime.UtcNow;
         _deviceRepository.Update(device);
         await _unitOfWork.SaveChangesAsync();
-        await _tokenCache.InvalidateAsync(serviceId, device.Id);
+        await _tokenCache.InvalidateAsync(serviceId, device.ExternalDeviceId);
     }
 
-    public async Task AdminDeleteAsync(long deviceId)
+    public async Task AdminDeleteAsync(string externalDeviceId)
     {
-        var device = await _deviceRepository.GetByIdAsync(deviceId);
+        var results = await _deviceRepository.FindAsync(d => d.ExternalDeviceId == externalDeviceId);
+        var device = results.FirstOrDefault();
         if (device == null)
             throw new SpmsException(ErrorCodes.DeviceNotFound, "존재하지 않는 디바이스입니다.", 404);
 
@@ -132,7 +135,7 @@ public class DeviceService : IDeviceService
         device.UpdatedAt = DateTime.UtcNow;
         _deviceRepository.Update(device);
         await _unitOfWork.SaveChangesAsync();
-        await _tokenCache.InvalidateAsync(device.ServiceId, device.Id);
+        await _tokenCache.InvalidateAsync(device.ServiceId, device.ExternalDeviceId);
     }
 
     public async Task<DeviceListResponseDto> GetListAsync(long? serviceId, DeviceListRequestDto request)
@@ -169,7 +172,7 @@ public class DeviceService : IDeviceService
         {
             Items = items.Select(d => new DeviceSummaryDto
             {
-                DeviceId = d.Id,
+                DeviceId = d.ExternalDeviceId,
                 Platform = d.Platform.ToString().ToLowerInvariant(),
                 Model = d.DeviceModel,
                 PushAgreed = d.PushAgreed,
@@ -259,7 +262,7 @@ public class DeviceService : IDeviceService
 
     public async Task SetTagsAsync(long serviceId, DeviceTagsRequestDto request)
     {
-        var device = await _deviceRepository.GetByIdAndServiceAsync(request.DeviceId, serviceId);
+        var device = await _deviceRepository.GetByExternalIdAndServiceAsync(request.DeviceId, serviceId);
         if (device == null)
             throw new SpmsException(ErrorCodes.DeviceNotFound, "존재하지 않는 디바이스입니다.", 404);
 
@@ -275,7 +278,7 @@ public class DeviceService : IDeviceService
 
     public async Task SetAgreeAsync(long serviceId, DeviceAgreeRequestDto request)
     {
-        var device = await _deviceRepository.GetByIdAndServiceAsync(request.DeviceId, serviceId);
+        var device = await _deviceRepository.GetByExternalIdAndServiceAsync(request.DeviceId, serviceId);
         if (device == null)
             throw new SpmsException(ErrorCodes.DeviceNotFound, "존재하지 않는 디바이스입니다.", 404);
 
@@ -286,7 +289,7 @@ public class DeviceService : IDeviceService
             device.MktAgreeUpdatedAt = DateTime.UtcNow;
         _deviceRepository.Update(device);
         await _unitOfWork.SaveChangesAsync();
-        await _tokenCache.InvalidateAsync(serviceId, device.Id);
+        await _tokenCache.InvalidateAsync(serviceId, device.ExternalDeviceId);
     }
 
     private static Platform ParsePlatform(string platform)

SPMS.Application/Services/PushService.cs

@@ -58,7 +58,7 @@ public class PushService : IPushService
             Target = new PushTargetDto
             {
                 Type = "device_ids",
-                Value = JsonSerializer.SerializeToElement(new[] { request.DeviceId })
+                Value = JsonSerializer.SerializeToElement(new[] { request.DeviceId })  // UUID string
             },
             CreatedBy = message.CreatedBy,
             CreatedAt = DateTime.UtcNow.ToString("o")
@@ -126,7 +126,7 @@ public class PushService : IPushService
         if (sendType != "single" && sendType != "tag")
             throw new SpmsException(ErrorCodes.BadRequest, "send_type은 single 또는 tag만 허용됩니다.", 400);
 
-        if (sendType == "single" && request.DeviceId == null)
+        if (sendType == "single" && string.IsNullOrWhiteSpace(request.DeviceId))
             throw new SpmsException(ErrorCodes.BadRequest, "send_type=single 시 device_id는 필수입니다.", 400);
 
         if (sendType == "tag" && (request.Tags == null || request.Tags.Count == 0))
@@ -144,7 +144,7 @@ public class PushService : IPushService
             target = new PushTargetDto
             {
                 Type = "device_ids",
-                Value = JsonSerializer.SerializeToElement(new[] { request.DeviceId!.Value })
+                Value = JsonSerializer.SerializeToElement(new[] { request.DeviceId! })  // UUID string
             };
         }
         else
@@ -252,7 +252,7 @@ public class PushService : IPushService
             {
                 SendId = l.Id,
                 MessageCode = l.Message?.MessageCode ?? string.Empty,
-                DeviceId = l.DeviceId,
+                DeviceId = l.Device?.ExternalDeviceId ?? l.DeviceId.ToString(),
                 Status = l.Status.ToString().ToLowerInvariant(),
                 FailReason = l.FailReason,
                 SentAt = l.SentAt
@@ -301,7 +301,7 @@ public class PushService : IPushService
                 Target = new PushTargetDto
                 {
                     Type = "device_ids",
-                    Value = JsonSerializer.SerializeToElement(new[] { row.DeviceId })
+                    Value = JsonSerializer.SerializeToElement(new[] { row.DeviceId })  // UUID string
                 },
                 CreatedBy = message.CreatedBy,
                 CreatedAt = DateTime.UtcNow.ToString("o"),
@@ -450,7 +450,8 @@ public class PushService : IPushService
             if (values.Length <= deviceIdIndex)
                 continue;
 
-            if (!long.TryParse(values[deviceIdIndex], out var deviceId))
+            var deviceId = values[deviceIdIndex];
+            if (string.IsNullOrWhiteSpace(deviceId))
                 continue;
 
             var variables = new Dictionary<string, string>();
@@ -468,7 +469,7 @@ public class PushService : IPushService
 
     private class CsvRow
     {
-        public long DeviceId { get; init; }
+        public string DeviceId { get; init; } = string.Empty;
         public Dictionary<string, string> Variables { get; init; } = new();
     }
 

SPMS.Domain/Entities/Device.cs

@@ -5,6 +5,7 @@ namespace SPMS.Domain.Entities;
 public class Device : BaseEntity
 {
     public long ServiceId { get; set; }
+    public string ExternalDeviceId { get; set; } = string.Empty;
     public string DeviceToken { get; set; } = string.Empty;
     public Platform Platform { get; set; }
     public string? AppVersion { get; set; }

SPMS.Domain/Interfaces/IDeviceRepository.cs

@@ -7,6 +7,7 @@ public interface IDeviceRepository : IRepository<Device>
 {
     Task<Device?> GetByServiceAndTokenAsync(long serviceId, string deviceToken);
     Task<Device?> GetByIdAndServiceAsync(long id, long serviceId);
+    Task<Device?> GetByExternalIdAndServiceAsync(string externalId, long serviceId);
     Task<int> GetActiveCountByServiceAsync(long serviceId);
     Task<IReadOnlyList<Device>> GetByPlatformAsync(long serviceId, Platform platform);
     Task<(IReadOnlyList<Device> Items, int TotalCount)> GetPagedAsync(

SPMS.Infrastructure/Caching/TokenCacheService.cs

@@ -25,7 +25,7 @@ public class TokenCacheService : ITokenCacheService
         _logger = logger;
     }
 
-    public async Task<CachedDeviceInfo?> GetDeviceInfoAsync(long serviceId, long deviceId)
+    public async Task<CachedDeviceInfo?> GetDeviceInfoAsync(long serviceId, string deviceId)
     {
         try
         {
@@ -45,7 +45,7 @@ public class TokenCacheService : ITokenCacheService
         }
     }
 
-    public async Task SetDeviceInfoAsync(long serviceId, long deviceId, CachedDeviceInfo info)
+    public async Task SetDeviceInfoAsync(long serviceId, string deviceId, CachedDeviceInfo info)
     {
         try
         {
@@ -60,7 +60,7 @@ public class TokenCacheService : ITokenCacheService
         }
     }
 
-    public async Task InvalidateAsync(long serviceId, long deviceId)
+    public async Task InvalidateAsync(long serviceId, string deviceId)
     {
         try
         {
@@ -97,6 +97,6 @@ public class TokenCacheService : ITokenCacheService
         }
     }
 
-    private string BuildKey(long serviceId, long deviceId) =>
+    private string BuildKey(long serviceId, string deviceId) =>
         $"{_settings.InstanceName}device:token:{serviceId}:{deviceId}";
 }

SPMS.Infrastructure/Migrations/20260303023033_AddExternalDeviceId.cs

@@ -0,0 +1,41 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace SPMS.Infrastructure.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddExternalDeviceId : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "ExternalDeviceId",
+                table: "Device",
+                type: "varchar(36)",
+                maxLength: 36,
+                nullable: false,
+                defaultValue: "")
+                .Annotation("MySql:CharSet", "utf8mb4");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Device_ServiceId_ExternalDeviceId",
+                table: "Device",
+                columns: new[] { "ServiceId", "ExternalDeviceId" },
+                unique: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_Device_ServiceId_ExternalDeviceId",
+                table: "Device");
+
+            migrationBuilder.DropColumn(
+                name: "ExternalDeviceId",
+                table: "Device");
+        }
+    }
+}

SPMS.Infrastructure/Migrations/AppDbContextModelSnapshot.cs

@@ -282,6 +282,11 @@ namespace SPMS.Infrastructure.Migrations
                         .HasMaxLength(255)
                         .HasColumnType("varchar(255)");
 
+                    b.Property<string>("ExternalDeviceId")
+                        .IsRequired()
+                        .HasMaxLength(36)
+                        .HasColumnType("varchar(36)");
+
                     b.Property<bool>("IsActive")
                         .ValueGeneratedOnAdd()
                         .HasColumnType("tinyint(1)")
@@ -316,6 +321,9 @@ namespace SPMS.Infrastructure.Migrations
 
                     b.HasIndex("ServiceId", "DeviceToken");
 
+                    b.HasIndex("ServiceId", "ExternalDeviceId")
+                        .IsUnique();
+
                     b.ToTable("Device", (string)null);
                 });
 

SPMS.Infrastructure/Persistence/Configurations/DeviceConfiguration.cs

@@ -14,6 +14,7 @@ public class DeviceConfiguration : IEntityTypeConfiguration<Device>
         builder.Property(e => e.Id).ValueGeneratedOnAdd();
 
         builder.Property(e => e.ServiceId).IsRequired();
+        builder.Property(e => e.ExternalDeviceId).HasMaxLength(36).IsRequired();
         builder.Property(e => e.DeviceToken).HasMaxLength(255).IsRequired();
         builder.Property(e => e.Platform).HasColumnType("tinyint").IsRequired();
         builder.Property(e => e.AppVersion).HasMaxLength(20);
@@ -33,6 +34,7 @@ public class DeviceConfiguration : IEntityTypeConfiguration<Device>
             .HasForeignKey(e => e.ServiceId)
             .OnDelete(DeleteBehavior.Restrict);
 
+        builder.HasIndex(e => new { e.ServiceId, e.ExternalDeviceId }).IsUnique();
         builder.HasIndex(e => new { e.ServiceId, e.DeviceToken });
     }
 }

SPMS.Infrastructure/Persistence/Repositories/DeviceRepository.cs

@@ -19,6 +19,11 @@ public class DeviceRepository : Repository<Device>, IDeviceRepository
         return await _dbSet.FirstOrDefaultAsync(d => d.Id == id && d.ServiceId == serviceId);
     }
 
+    public async Task<Device?> GetByExternalIdAndServiceAsync(string externalId, long serviceId)
+    {
+        return await _dbSet.FirstOrDefaultAsync(d => d.ExternalDeviceId == externalId && d.ServiceId == serviceId);
+    }
+
     public async Task<int> GetActiveCountByServiceAsync(long serviceId)
     {
         return await _dbSet.CountAsync(d => d.ServiceId == serviceId && d.IsActive);

SPMS.Infrastructure/Persistence/Repositories/PushSendLogRepository.cs

@@ -17,6 +17,7 @@ public class PushSendLogRepository : Repository<PushSendLog>, IPushSendLogReposi
     {
         var query = _dbSet
             .Include(l => l.Message)
+            .Include(l => l.Device)
             .Where(l => l.ServiceId == serviceId);
 
         if (messageId.HasValue)

SPMS.Infrastructure/Workers/DeadTokenCleanupWorker.cs

@@ -110,7 +110,7 @@ public class DeadTokenCleanupWorker : BackgroundService
         {
             var batch = await context.Set<Device>()
                 .Where(d => !d.IsActive && d.UpdatedAt < cutoffUtc)
-                .Select(d => new { d.Id, d.ServiceId })
+                .Select(d => new { d.Id, d.ServiceId, d.ExternalDeviceId })
                 .Take(BatchSize)
                 .ToListAsync(stoppingToken);
 
@@ -130,7 +130,7 @@ public class DeadTokenCleanupWorker : BackgroundService
 
             // 삭제된 디바이스의 Redis 캐시 무효화
             foreach (var item in batch)
-                await _tokenCache.InvalidateAsync(item.ServiceId, item.Id);
+                await _tokenCache.InvalidateAsync(item.ServiceId, item.ExternalDeviceId);
 
             _logger.LogInformation("DeadTokenCleanupWorker 배치 삭제: {BatchCount}건 (누적: {TotalDeleted}건), 캐시 무효화 완료",
                 deletedInBatch, totalDeleted);

SPMS.Infrastructure/Workers/PushWorker.cs

@@ -310,21 +310,21 @@ public class PushWorker : BackgroundService
         {
             case "single":
             {
-                var deviceIds = ParseDeviceIds(message.Target);
+                var externalIds = ParseExternalDeviceIds(message.Target);
-                if (deviceIds.Count == 0) return [];
+                if (externalIds.Count == 0) return [];
 
                 var devices = new List<Device>();
-                foreach (var id in deviceIds)
+                foreach (var externalId in externalIds)
                 {
-                    // Redis 캐시 우선 조회
+                    // Redis 캐시 우선 조회 (ExternalDeviceId 기준)
-                    var cached = await _tokenCache.GetDeviceInfoAsync(message.ServiceId, id);
+                    var cached = await _tokenCache.GetDeviceInfoAsync(message.ServiceId, externalId);
                     if (cached != null)
                     {
                         if (cached.IsActive && cached.PushAgreed)
                         {
                             devices.Add(new Device
                             {
-                                Id = id,
+                                ExternalDeviceId = externalId,
                                 ServiceId = message.ServiceId,
                                 DeviceToken = cached.Token,
                                 Platform = (Platform)cached.Platform,
@@ -336,10 +336,10 @@ public class PushWorker : BackgroundService
                     }
 
                     // 캐시 미스 → DB 조회 후 캐시 저장
-                    var device = await deviceRepo.GetByIdAndServiceAsync(id, message.ServiceId);
+                    var device = await deviceRepo.GetByExternalIdAndServiceAsync(externalId, message.ServiceId);
                     if (device != null)
                     {
-                        await _tokenCache.SetDeviceInfoAsync(message.ServiceId, id,
+                        await _tokenCache.SetDeviceInfoAsync(message.ServiceId, externalId,
                             new CachedDeviceInfo(device.DeviceToken, (int)device.Platform,
                                 device.IsActive, device.PushAgreed));
 
@@ -383,7 +383,7 @@ public class PushWorker : BackgroundService
         }
     }
 
-    private static List<long> ParseDeviceIds(PushTargetDto target)
+    private static List<string> ParseExternalDeviceIds(PushTargetDto target)
     {
         if (target.Value == null) return [];
 
@@ -392,8 +392,8 @@ public class PushWorker : BackgroundService
             if (target.Value.Value.ValueKind == JsonValueKind.Array)
             {
                 return target.Value.Value.EnumerateArray()
-                    .Where(e => e.ValueKind == JsonValueKind.Number)
+                    .Where(e => e.ValueKind == JsonValueKind.String)
-                    .Select(e => e.GetInt64())
+                    .Select(e => e.GetString()!)
                     .ToList();
             }
         }