diff --git a/backend/lib/GitSheets.js b/backend/lib/GitSheets.js
index c9c42ae..3a6adf3 100644
--- a/backend/lib/GitSheets.js
+++ b/backend/lib/GitSheets.js
@@ -265,6 +265,41 @@ module.exports = class GitSheets {
     await this.git.branch({D: true}, dstRef); // force delete in case srcRef is not checked out
   }
 
+  async createTransaction (parentRef) {
+    const pathTemplate = await this.getConfigItem(parentRef, 'path');
+    const treeObject = await this._createTreeFromRef(parentRef);
+    const gitSheets = this;
+
+    // TODO: Use a class or something, rather than generating this code each transaction
+    return {
+      upsert: function upsert (data) {
+        const path = gitSheets._renderTemplate(pathTemplate, data);
+        const contents = gitSheets._serialize(data);
+        // TODO: Wrap errors
+        return treeObject.writeChild(`${path}.toml`, contents);
+      },
+      async save (saveToBranch = parentRef) {
+        // TODO: Wrap errors
+        const treeHash = await treeObject.write();
+
+        if (saveToBranch && saveToBranch === parentRef) { // TODO: check if branch exists instead
+          await gitSheets._saveTreeToExistingBranch({
+            treeHash,
+            branch: saveToBranch,
+            msg: 'import to existing branch',
+          });
+        } else if (saveToBranch) {
+          await gitSheets._saveTreeToNewBranch({
+            treeHash,
+            parentRef,
+            branch: saveToBranch,
+            msg: 'import to new branch',
+          });
+        }
+      },
+    };
+  }
+
   _isDataBlob ([key, blob]) {
     return !key.startsWith('.gitsheets/') && key.endsWith('.toml') && blob instanceof BlobObject;
   }
diff --git a/backend/test/GitSheets.spec.js b/backend/test/GitSheets.spec.js
index 0817cde..12ec662 100644
--- a/backend/test/GitSheets.spec.js
+++ b/backend/test/GitSheets.spec.js
@@ -357,6 +357,34 @@ describe('GitSheets lib', () => {
         .toThrow(MergeError);
     });
   });
+
+  describe.only('Transaction', () => {
+    it('upserts on top of branch', async () => {
+      await gitSheets.setConfigItem('master', 'path', '{{id}}');
+
+      const txn = await gitSheets.createTransaction('master');
+      await txn.upsert(sampleData.initial[0]);
+      await txn.upsert(sampleData.initial[1]);
+      await txn.save();
+
+      const response = await gitSheets.git.lsTree('master');
+      const tree = parseTree(response);
+
+      const blobs = tree.filter((item) => item.type === 'blob');
+      expect(blobs.length).toBe(2);
+
+      await Promise.all(blobs.map(verifyBlob));
+
+      async function verifyBlob ({ hash, file }) {
+        const sampleDataItem = sampleData.initial.find((item) => item.id === file.substr(0, file.length - 5));
+        expect(sampleDataItem).toBeDefined();
+
+        const contents = await gitSheets.git.catFile('blob', hash);
+        const data = gitSheets._deserialize(contents);
+        expect(data).toEqual(sampleDataItem);
+      }
+    })
+  })
 });
 
 function parseTree (treeOutput) {