diff --git a/keyserver/src/responders/user-responders.js b/keyserver/src/responders/user-responders.js
--- a/keyserver/src/responders/user-responders.js
+++ b/keyserver/src/responders/user-responders.js
@@ -24,6 +24,7 @@
   notificationTypeValues,
   logInActionSources,
 } from 'lib/types/account-types';
+import type { CalendarQuery } from 'lib/types/entry-types.js';
 import { defaultNumberPerThread } from 'lib/types/message-types';
 import type { SIWEAuthRequest, SIWEMessage } from 'lib/types/siwe-types.js';
 import type {
@@ -189,66 +190,19 @@
   return await createAccount(viewer, request);
 }
 
-const logInRequestInputValidator = tShape({
-  username: t.maybe(t.String),
-  usernameOrEmail: t.maybe(t.union([tEmail, tOldValidUsername])),
-  password: tPassword,
-  watchedIDs: t.list(t.String),
-  calendarQuery: t.maybe(entryQueryInputValidator),
-  deviceTokenUpdateRequest: t.maybe(deviceTokenUpdateRequestInputValidator),
-  platformDetails: tPlatformDetails,
-  source: t.maybe(t.enums.of(values(logInActionSources))),
-});
-
-async function logInResponder(
+async function processSuccessfulLogin(
   viewer: Viewer,
   input: any,
-): Promise<LogInResponse> {
-  await validateInput(viewer, logInRequestInputValidator, input);
+  userID: string,
+  calendarQuery: ?CalendarQuery,
+) {
   const request: LogInRequest = input;
-
-  const calendarQuery = request.calendarQuery
-    ? normalizeCalendarQuery(request.calendarQuery)
-    : null;
-  const promises = {};
-  if (calendarQuery) {
-    promises.verifyCalendarQueryThreadIDs = verifyCalendarQueryThreadIDs(
-      calendarQuery,
-    );
-  }
-  const username = request.username ?? request.usernameOrEmail;
-  if (!username) {
-    throw new ServerError('invalid_parameters');
-  }
-  const userQuery = SQL`
-    SELECT id, hash, username
-    FROM users
-    WHERE LCASE(username) = LCASE(${username})
-  `;
-  promises.userQuery = dbQuery(userQuery);
-  const {
-    userQuery: [userResult],
-  } = await promiseAll(promises);
-
-  if (userResult.length === 0) {
-    throw new ServerError('invalid_parameters');
-  }
-  const userRow = userResult[0];
-  if (!userRow.hash || !bcrypt.compareSync(request.password, userRow.hash)) {
-    if (hasMinCodeVersion(viewer.platformDetails, 99999)) {
-      throw new ServerError('invalid_parameters');
-    } else {
-      throw new ServerError('invalid_credentials');
-    }
-  }
-  const id = userRow.id.toString();
-
   const newServerTime = Date.now();
   const deviceToken = request.deviceTokenUpdateRequest
     ? request.deviceTokenUpdateRequest.deviceToken
     : viewer.deviceToken;
   const [userViewerData] = await Promise.all([
-    createNewUserCookie(id, {
+    createNewUserCookie(userID, {
       platformDetails: request.platformDetails,
       deviceToken,
     }),
@@ -297,6 +251,62 @@
   return response;
 }
 
+const logInRequestInputValidator = tShape({
+  username: t.maybe(t.String),
+  usernameOrEmail: t.maybe(t.union([tEmail, tOldValidUsername])),
+  password: tPassword,
+  watchedIDs: t.list(t.String),
+  calendarQuery: t.maybe(entryQueryInputValidator),
+  deviceTokenUpdateRequest: t.maybe(deviceTokenUpdateRequestInputValidator),
+  platformDetails: tPlatformDetails,
+  source: t.maybe(t.enums.of(values(logInActionSources))),
+});
+
+async function logInResponder(
+  viewer: Viewer,
+  input: any,
+): Promise<LogInResponse> {
+  await validateInput(viewer, logInRequestInputValidator, input);
+  const request: LogInRequest = input;
+
+  const calendarQuery = request.calendarQuery
+    ? normalizeCalendarQuery(request.calendarQuery)
+    : null;
+  const promises = {};
+  if (calendarQuery) {
+    promises.verifyCalendarQueryThreadIDs = verifyCalendarQueryThreadIDs(
+      calendarQuery,
+    );
+  }
+  const username = request.username ?? request.usernameOrEmail;
+  if (!username) {
+    throw new ServerError('invalid_parameters');
+  }
+  const userQuery = SQL`
+    SELECT id, hash, username
+    FROM users
+    WHERE LCASE(username) = LCASE(${username})
+  `;
+  promises.userQuery = dbQuery(userQuery);
+  const {
+    userQuery: [userResult],
+  } = await promiseAll(promises);
+
+  if (userResult.length === 0) {
+    throw new ServerError('invalid_parameters');
+  }
+  const userRow = userResult[0];
+  if (!userRow.hash || !bcrypt.compareSync(request.password, userRow.hash)) {
+    if (hasMinCodeVersion(viewer.platformDetails, 99999)) {
+      throw new ServerError('invalid_parameters');
+    } else {
+      throw new ServerError('invalid_credentials');
+    }
+  }
+  const id = userRow.id.toString();
+  return await processSuccessfulLogin(viewer, input, id, calendarQuery);
+}
+
 const siweAuthRequestInputValidator = tShape({
   signature: t.String,
   message: t.String,