diff --git a/src/origdatablocks/origdatablocks.controller.spec.ts b/src/origdatablocks/origdatablocks.controller.spec.ts
index 96004b284..7a86a117e 100644
--- a/src/origdatablocks/origdatablocks.controller.spec.ts
+++ b/src/origdatablocks/origdatablocks.controller.spec.ts
@@ -10,15 +10,19 @@ import { Request } from "express";
 class OrigDatablocksServiceMock {
   findOne = jest.fn();
   findByIdAndUpdate = jest.fn();
+  aggregateSizeAndFileCount = jest.fn();
 }
 
-class DatasetsServiceMock {}
+class DatasetsServiceMock {
+  findByIdAndUpdate = jest.fn();
+}
 
 class CaslAbilityFactoryMock {}
 
 describe("OrigDatablocksController", () => {
   let controller: OrigDatablocksController;
   let origDatablocksService: OrigDatablocksServiceMock;
+  let datasetsService: DatasetsServiceMock;
 
   beforeEach(async () => {
     const module: TestingModule = await Test.createTestingModule({
@@ -34,10 +38,10 @@ describe("OrigDatablocksController", () => {
     controller = module.get<OrigDatablocksController>(OrigDatablocksController);
     origDatablocksService = module.get<OrigDatablocksService>(
       OrigDatablocksService,
-    );
-
-    // Mock internal methods
-    controller["updateDatasetSizeAndFiles"] = jest.fn();
+    ) as unknown as OrigDatablocksServiceMock;
+    datasetsService = module.get<DatasetsService>(
+      DatasetsService,
+    ) as unknown as DatasetsServiceMock;
   });
 
   it("should be defined", () => {
@@ -55,6 +59,11 @@ describe("OrigDatablocksController", () => {
       datasetId: "ds1",
     };
 
+    beforeEach(() => {
+      // Isolate the update handler from the side-effect helper
+      controller["updateDatasetSizeAndFiles"] = jest.fn();
+    });
+
     it("should throw NotFoundException if datablock not found before update", async () => {
       origDatablocksService.findOne.mockResolvedValue(null);
 
@@ -160,4 +169,40 @@ describe("OrigDatablocksController", () => {
       });
     });
   });
+
+  describe("updateDatasetSizeAndFiles", () => {
+    it("should use aggregateSizeAndFileCount and update the dataset", async () => {
+      origDatablocksService.aggregateSizeAndFileCount.mockResolvedValue({
+        size: 2000,
+        numberOfFiles: 5,
+      });
+
+      await controller["updateDatasetSizeAndFiles"]("testPid");
+
+      expect(
+        origDatablocksService.aggregateSizeAndFileCount,
+      ).toHaveBeenCalledWith("testPid");
+      expect(datasetsService.findByIdAndUpdate).toHaveBeenCalledWith(
+        "testPid",
+        {
+          size: 2000,
+          numberOfFiles: 5,
+        },
+      );
+    });
+
+    it("should propagate zero totals when no origdatablocks exist", async () => {
+      origDatablocksService.aggregateSizeAndFileCount.mockResolvedValue({
+        size: 0,
+        numberOfFiles: 0,
+      });
+
+      await controller["updateDatasetSizeAndFiles"]("emptyPid");
+
+      expect(datasetsService.findByIdAndUpdate).toHaveBeenCalledWith(
+        "emptyPid",
+        { size: 0, numberOfFiles: 0 },
+      );
+    });
+  });
 });
diff --git a/src/origdatablocks/origdatablocks.controller.ts b/src/origdatablocks/origdatablocks.controller.ts
index 33d99e5dd..7bfefce7d 100644
--- a/src/origdatablocks/origdatablocks.controller.ts
+++ b/src/origdatablocks/origdatablocks.controller.ts
@@ -40,7 +40,6 @@ import { IOrigDatablockFields } from "./interfaces/origdatablocks.interface";
 import { plainToInstance } from "class-transformer";
 import { validate, ValidationError } from "class-validator";
 import { DatasetsService } from "src/datasets/datasets.service";
-import { PartialUpdateDatasetDto } from "src/datasets/dto/update-dataset.dto";
 import { filterDescription, filterExample, parseDate } from "src/common/utils";
 import { JWTUser } from "src/auth/interfaces/jwt-user.interface";
 import { DatasetClass } from "src/datasets/schemas/dataset.schema";
@@ -213,22 +212,10 @@ export class OrigDatablocksController {
   }
 
   async updateDatasetSizeAndFiles(pid: string) {
-    // updates datasets size
-    const parsedFilters: IFilters<OrigDatablockDocument, IOrigDatablockFields> =
-      { where: { datasetId: pid } };
-    const datasetOrigdatablocks =
-      await this.origDatablocksService.findAll(parsedFilters);
-
-    const updateDatasetDto: PartialUpdateDatasetDto = {
-      size: datasetOrigdatablocks
-        .map((od) => od.size)
-        .reduce((ps, a) => ps + a, 0),
-      numberOfFiles: datasetOrigdatablocks
-        .map((od) => od.dataFileList.length)
-        .reduce((ps, a) => ps + a, 0),
-    };
+    const { size, numberOfFiles } =
+      await this.origDatablocksService.aggregateSizeAndFileCount(pid);
 
-    await this.datasetsService.findByIdAndUpdate(pid, updateDatasetDto);
+    await this.datasetsService.findByIdAndUpdate(pid, { size, numberOfFiles });
   }
 
   @UseGuards(PoliciesGuard)
diff --git a/src/origdatablocks/origdatablocks.service.spec.ts b/src/origdatablocks/origdatablocks.service.spec.ts
index 7d5ca7999..5aff25fef 100644
--- a/src/origdatablocks/origdatablocks.service.spec.ts
+++ b/src/origdatablocks/origdatablocks.service.spec.ts
@@ -47,6 +47,7 @@ describe("OrigdatablocksService", () => {
             find: jest.fn(),
             create: jest.fn(),
             exec: jest.fn(),
+            aggregate: jest.fn(),
           },
         },
       ],
@@ -61,4 +62,44 @@ describe("OrigdatablocksService", () => {
   it("should be defined", () => {
     expect(service).toBeDefined();
   });
+
+  describe("aggregateSizeAndFileCount", () => {
+    it("should return summed size and file count from origdatablocks", async () => {
+      (model.aggregate as jest.Mock).mockReturnValue({
+        exec: jest
+          .fn()
+          .mockResolvedValue([{ _id: null, size: 5000, numberOfFiles: 3 }]),
+      });
+
+      const result = await service.aggregateSizeAndFileCount("testPid");
+
+      expect(result).toEqual({ size: 5000, numberOfFiles: 3 });
+    });
+
+    it("should return zeros when no origdatablocks exist for the dataset", async () => {
+      (model.aggregate as jest.Mock).mockReturnValue({
+        exec: jest.fn().mockResolvedValue([]),
+      });
+
+      const result = await service.aggregateSizeAndFileCount("emptyPid");
+
+      expect(result).toEqual({ size: 0, numberOfFiles: 0 });
+    });
+
+    it("should match on the given datasetId", async () => {
+      (model.aggregate as jest.Mock).mockReturnValue({
+        exec: jest
+          .fn()
+          .mockResolvedValue([{ _id: null, size: 0, numberOfFiles: 0 }]),
+      });
+
+      await service.aggregateSizeAndFileCount("ds123");
+
+      expect(model.aggregate).toHaveBeenCalledWith(
+        expect.arrayContaining([
+          expect.objectContaining({ $match: { datasetId: "ds123" } }),
+        ]),
+      );
+    });
+  });
 });
diff --git a/src/origdatablocks/origdatablocks.service.ts b/src/origdatablocks/origdatablocks.service.ts
index 9d0e793f4..93fa40012 100644
--- a/src/origdatablocks/origdatablocks.service.ts
+++ b/src/origdatablocks/origdatablocks.service.ts
@@ -382,4 +382,26 @@ export class OrigDatablocksService {
       .exec();
     return { count };
   }
+
+  async aggregateSizeAndFileCount(
+    datasetId: string,
+  ): Promise<{ size: number; numberOfFiles: number }> {
+    const [result] = await this.origDatablockModel
+      .aggregate<{ size: number; numberOfFiles: number }>([
+        { $match: { datasetId } },
+        {
+          $group: {
+            _id: null,
+            size: { $sum: "$size" },
+            numberOfFiles: {
+              $sum: { $size: { $ifNull: ["$dataFileList", []] } },
+            },
+          },
+        },
+      ])
+      .exec();
+    return result
+      ? { size: result.size, numberOfFiles: result.numberOfFiles }
+      : { size: 0, numberOfFiles: 0 };
+  }
 }