diff --git a/src/domain/documentRequestFactory.ts b/src/domain/documentRequestFactory.ts
new file mode 100644
index 0000000..20f826e
--- /dev/null
+++ b/src/domain/documentRequestFactory.ts
@@ -0,0 +1,71 @@
+import AWS, { S3 } from 'aws-sdk';
+import { APIGatewayProxyResult } from 'aws-lambda';
+import getCertificate from './getCertificate';
+import getLetter from './getLetter';
+import getPlate from './getPlate';
+
+const {
+  NODE_ENV, BUCKET, BRANCH,
+} = process.env;
+
+export default async (vin: string, testNumber: string, plateSerialNumber: string, systemNumber: string): Promise<APIGatewayProxyResult> => {
+  const s3 = new S3(
+    process.env.IS_OFFLINE && {
+      s3ForcePathStyle: true,
+      // You will need to create your s3local profile (~/.aws/credentials) if you are not using any
+      accessKeyId: 'S3RVER',
+      secretAccessKey: 'S3RVER',
+      endpoint: new AWS.Endpoint('http://localhost:4569'),
+    },
+  );
+
+  const isCertificate = vin && testNumber && !plateSerialNumber && !systemNumber;
+  const isPlate = plateSerialNumber && !vin && !testNumber && !systemNumber;
+  const isLetter = !plateSerialNumber && vin && !testNumber && systemNumber;
+
+  if (isCertificate) {
+    console.info('Calling cert service');
+    return getCertificate(
+      {
+        vin,
+        testNumber,
+      },
+      s3,
+      `cvs-cert-${BUCKET}`,
+      BRANCH,
+      NODE_ENV,
+    );
+  }
+
+  if (isPlate) {
+    console.info('Calling plate service');
+    return getPlate(
+      {
+        plateSerialNumber,
+      },
+      s3,
+      `cvs-cert-${BUCKET}`,
+      BRANCH,
+      NODE_ENV,
+    );
+  }
+
+  if (isLetter) {
+    console.info('Calling letter service');
+    return getLetter(
+      {
+        vin,
+        systemNumber,
+      },
+      s3,
+      `cvs-cert-${BUCKET}`,
+      BRANCH,
+      NODE_ENV,
+    );
+  }
+
+  return Promise.resolve({
+    statusCode: 400,
+    body: '',
+  });
+};
diff --git a/src/infrastructure/api/index.ts b/src/infrastructure/api/index.ts
index 3aafa61..e381cd1 100644
--- a/src/infrastructure/api/index.ts
+++ b/src/infrastructure/api/index.ts
@@ -1,14 +1,9 @@
-import AWS, { S3 } from 'aws-sdk';
 import express, { Request, Response } from 'express';
-import getCertificate from '../../domain/getCertificate';
-import getLetter from '../../domain/getLetter';
-import getPlate from '../../domain/getPlate';
+import documentRequestFactory from '../../domain/documentRequestFactory';
 
 const app = express();
 
-const {
-  API_VERSION, NODE_ENV, BUCKET, BRANCH,
-} = process.env;
+const { API_VERSION } = process.env;
 
 // Debug router before we start proxying  requests from /v<x> psth
 app.get('/', (_request, res) => {
@@ -20,111 +15,24 @@ app.get('/version', (_request, res) => {
 });
 
 app.get('/document-retrieval', (req: Request, res: Response) => {
-  if (req.query.vinNumber && req.query.testNumber && !req.query.plateSerialNumber && !req.query.systemNumber) {
-    console.info('Calling cert service');
-
-    getCertificate(
-      {
-        vin: req.query.vinNumber as string,
-        testNumber: req.query.testNumber as string,
-      },
-      new S3(
-        process.env.IS_OFFLINE && {
-          s3ForcePathStyle: true,
-          // You will need to create your s3local profile (~/.aws/credentials) if you are not using any
-          accessKeyId: 'S3RVER',
-          secretAccessKey: 'S3RVER',
-          endpoint: new AWS.Endpoint('http://localhost:4569'),
-        },
-      ),
-      `cvs-cert-${BUCKET}`,
-      BRANCH,
-      NODE_ENV,
-    )
-      .then(({ statusCode, headers, body }) => {
-        res.status(statusCode);
-
-        if (headers) {
-          res.header(headers);
-        }
-
-        res.send(body);
-      })
-      .catch((e: Error) => {
-        console.error(e.message);
-        res.status(500).send(e.message);
-      });
-  } else if (req.query.plateSerialNumber && !req.query.vinNumber && !req.query.testNumber && !req.query.systemNumber) {
-    console.info('Calling plate service');
-
-    getPlate(
-      {
-        plateSerialNumber: req.query.plateSerialNumber as string,
-      },
-      new S3(
-        process.env.IS_OFFLINE && {
-          s3ForcePathStyle: true,
-          // You will need to create your s3local profile (~/.aws/credentials) if you are not using any
-          accessKeyId: 'S3RVER',
-          secretAccessKey: 'S3RVER',
-          endpoint: new AWS.Endpoint('http://localhost:4569'),
-        },
-      ),
-      `cvs-cert-${BUCKET}`,
-      BRANCH,
-      NODE_ENV,
-    )
-      .then(({ statusCode, headers, body }) => {
-        res.status(statusCode);
-
-        if (headers) {
-          res.header(headers);
-        }
-
-        res.send(body);
-      })
-      .catch((e: Error) => {
-        console.error(e.message);
-        res.status(500).send(e.message);
-      });
-  } else if (!req.query.plateSerialNumber && req.query.vinNumber && !req.query.testNumber && req.query.systemNumber) {
-    console.info('Calling letter service');
-
-    
-    getLetter(
-      {
-        vin: req.query.vinNumber as string,
-        systemNumber: req.query.systemNumber as string,
-      },
-      new S3(
-        process.env.IS_OFFLINE && {
-          s3ForcePathStyle: true,
-          // You will need to create your s3local profile (~/.aws/credentials) if you are not using any
-          accessKeyId: 'S3RVER',
-          secretAccessKey: 'S3RVER',
-          endpoint: new AWS.Endpoint('http://localhost:4569'),
-        },
-      ),
-      `cvs-cert-${BUCKET}`,
-      BRANCH,
-      NODE_ENV,
-    )
-      .then(({ statusCode, headers, body }) => {
-        res.status(statusCode);
-
-        if (headers) {
-          res.header(headers);
-        }
-
-        res.send(body);
-      })
-      .catch((e: Error) => {
-        console.error(e.message);
-        res.status(500).send(e.message);
-      });
-  } else {
-    res.status(400).end();
-  }
+  const {
+    vinNumber, plateSerialNumber, testNumber, systemNumber,
+  } = req.query;
+
+  documentRequestFactory(vinNumber as string, testNumber as string, plateSerialNumber as string, systemNumber as string)
+    .then(({ statusCode, headers, body }) => {
+      res.status(statusCode);
+
+      if (headers) {
+        res.header(headers);
+      }
+
+      res.send(body);
+    })
+    .catch((e: Error) => {
+      console.error(e.message);
+      res.status(500).send(e.message);
+    });
 });
 
 app.all('/document-retrieval', (_request, res: Response) => {