diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -3706,6 +3706,7 @@
     'PhabricatorSettingsTimezoneController' => 'applications/settings/controller/PhabricatorSettingsTimezoneController.php',
     'PhabricatorSetupCheck' => 'applications/config/check/PhabricatorSetupCheck.php',
     'PhabricatorSetupCheckTestCase' => 'applications/config/check/__tests__/PhabricatorSetupCheckTestCase.php',
+    'PhabricatorSetupEngine' => 'applications/config/engine/PhabricatorSetupEngine.php',
     'PhabricatorSetupIssue' => 'applications/config/issue/PhabricatorSetupIssue.php',
     'PhabricatorSetupIssueUIExample' => 'applications/uiexample/examples/PhabricatorSetupIssueUIExample.php',
     'PhabricatorSetupIssueView' => 'applications/config/view/PhabricatorSetupIssueView.php',
@@ -8868,6 +8869,7 @@
     'PhabricatorSettingsTimezoneController' => 'PhabricatorController',
     'PhabricatorSetupCheck' => 'Phobject',
     'PhabricatorSetupCheckTestCase' => 'PhabricatorTestCase',
+    'PhabricatorSetupEngine' => 'Phobject',
     'PhabricatorSetupIssue' => 'Phobject',
     'PhabricatorSetupIssueUIExample' => 'PhabricatorUIExample',
     'PhabricatorSetupIssueView' => 'AphrontView',
diff --git a/src/applications/config/check/PhabricatorSetupCheck.php b/src/applications/config/check/PhabricatorSetupCheck.php
--- a/src/applications/config/check/PhabricatorSetupCheck.php
+++ b/src/applications/config/check/PhabricatorSetupCheck.php
@@ -68,6 +68,39 @@
     return $cache->getKey('phabricator.setup.issue-keys');
   }
 
+  final public static function resetSetupState() {
+    $cache = PhabricatorCaches::getSetupCache();
+    $cache->deleteKey('phabricator.setup.issue-keys');
+
+    $server_cache = PhabricatorCaches::getServerStateCache();
+    $server_cache->deleteKey('phabricator.in-flight');
+
+    $use_scope = AphrontWriteGuard::isGuardActive();
+    if ($use_scope) {
+      $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
+    } else {
+      AphrontWriteGuard::allowDangerousUnguardedWrites(true);
+    }
+
+    $caught = null;
+    try {
+      $db_cache = new PhabricatorKeyValueDatabaseCache();
+      $db_cache->deleteKey('phabricator.setup.issue-keys');
+    } catch (Exception $ex) {
+      $caught = $ex;
+    }
+
+    if ($use_scope) {
+      unset($unguarded);
+    } else {
+      AphrontWriteGuard::allowDangerousUnguardedWrites(false);
+    }
+
+    if ($caught) {
+      throw $caught;
+    }
+  }
+
   final public static function setOpenSetupIssueKeys(
     array $keys,
     $update_database) {
@@ -161,14 +194,11 @@
   final public static function willProcessRequest() {
     $issue_keys = self::getOpenSetupIssueKeys();
     if ($issue_keys === null) {
-      $issues = self::runNormalChecks();
-      foreach ($issues as $issue) {
-        if ($issue->getIsFatal()) {
-          return self::newIssueResponse($issue);
-        }
+      $engine = new PhabricatorSetupEngine();
+      $response = $engine->execute();
+      if ($response) {
+        return $response;
       }
-      $issue_keys = self::getUnignoredIssueKeys($issues);
-      self::setOpenSetupIssueKeys($issue_keys, $update_database = true);
     } else if ($issue_keys) {
       // If Phabricator is configured in a cluster with multiple web devices,
       // we can end up with setup issues cached on every device. This can cause
diff --git a/src/applications/config/controller/PhabricatorConfigIssueListController.php b/src/applications/config/controller/PhabricatorConfigIssueListController.php
--- a/src/applications/config/controller/PhabricatorConfigIssueListController.php
+++ b/src/applications/config/controller/PhabricatorConfigIssueListController.php
@@ -9,10 +9,12 @@
     $nav = $this->buildSideNavView();
     $nav->selectFilter('issue/');
 
-    $issues = PhabricatorSetupCheck::runNormalChecks();
-    PhabricatorSetupCheck::setOpenSetupIssueKeys(
-      PhabricatorSetupCheck::getUnignoredIssueKeys($issues),
-      $update_database = true);
+    $engine = new PhabricatorSetupEngine();
+    $response = $engine->execute();
+    if ($response) {
+      return $response;
+    }
+    $issues = $engine->getIssues();
 
     $important = $this->buildIssueList(
       $issues,
diff --git a/src/applications/config/controller/PhabricatorConfigIssuePanelController.php b/src/applications/config/controller/PhabricatorConfigIssuePanelController.php
--- a/src/applications/config/controller/PhabricatorConfigIssuePanelController.php
+++ b/src/applications/config/controller/PhabricatorConfigIssuePanelController.php
@@ -5,11 +5,14 @@
 
   public function handleRequest(AphrontRequest $request) {
     $viewer = $request->getViewer();
-    $open_items = PhabricatorSetupCheck::getOpenSetupIssueKeys();
-    $issues = PhabricatorSetupCheck::runNormalChecks();
-    PhabricatorSetupCheck::setOpenSetupIssueKeys(
-      PhabricatorSetupCheck::getUnignoredIssueKeys($issues),
-      $update_database = true);
+
+    $engine = new PhabricatorSetupEngine();
+    $response = $engine->execute();
+    if ($response) {
+      return $response;
+    }
+    $issues = $engine->getIssues();
+    $unresolved_count = count($engine->getUnresolvedIssues());
 
     if ($issues) {
       require_celerity_resource('phabricator-notification-menu-css');
@@ -55,8 +58,6 @@
         pht('Unresolved Setup Issues')),
       $content);
 
-    $unresolved_count = count($open_items);
-
     $json = array(
       'content' => $content,
       'number'  => (int)$unresolved_count,
diff --git a/src/applications/config/controller/PhabricatorConfigIssueViewController.php b/src/applications/config/controller/PhabricatorConfigIssueViewController.php
--- a/src/applications/config/controller/PhabricatorConfigIssueViewController.php
+++ b/src/applications/config/controller/PhabricatorConfigIssueViewController.php
@@ -7,10 +7,12 @@
     $viewer = $request->getViewer();
     $issue_key = $request->getURIData('key');
 
-    $issues = PhabricatorSetupCheck::runNormalChecks();
-    PhabricatorSetupCheck::setOpenSetupIssueKeys(
-      PhabricatorSetupCheck::getUnignoredIssueKeys($issues),
-      $update_database = true);
+    $engine = new PhabricatorSetupEngine();
+    $response = $engine->execute();
+    if ($response) {
+      return $response;
+    }
+    $issues = $engine->getIssues();
 
     $nav = $this->buildSideNavView();
     $nav->selectFilter('issue/');
diff --git a/src/applications/config/engine/PhabricatorSetupEngine.php b/src/applications/config/engine/PhabricatorSetupEngine.php
new file mode 100644
--- /dev/null
+++ b/src/applications/config/engine/PhabricatorSetupEngine.php
@@ -0,0 +1,64 @@
+<?php
+
+final class PhabricatorSetupEngine
+  extends Phobject {
+
+  private $issues;
+
+  public function getIssues() {
+    if ($this->issues === null) {
+      throw new PhutilInvalidStateException('execute');
+    }
+
+    return $this->issues;
+  }
+
+  public function getUnresolvedIssues() {
+    $issues = $this->getIssues();
+    $issues = mpull($issues, null, 'getIssueKey');
+
+    $unresolved_keys = PhabricatorSetupCheck::getUnignoredIssueKeys($issues);
+
+    return array_select_keys($issues, $unresolved_keys);
+  }
+
+  public function execute() {
+    $issues = PhabricatorSetupCheck::runNormalChecks();
+
+    $fatal_issue = null;
+    foreach ($issues as $issue) {
+      if ($issue->getIsFatal()) {
+        $fatal_issue = $issue;
+        break;
+      }
+    }
+
+    if ($fatal_issue) {
+      // If we've discovered a fatal, we reset any in-flight state to push
+      // web hosts out of service.
+
+      // This can happen if Phabricator starts during a disaster and some
+      // databases can not be reached. We allow Phabricator to start up in
+      // this situation, since it may still be able to usefully serve requests
+      // without risk to data.
+
+      // However, if databases later become reachable and we learn that they
+      // are fatally misconfigured, we want to tear the world down again
+      // because data may be at risk.
+      PhabricatorSetupCheck::resetSetupState();
+
+      return PhabricatorSetupCheck::newIssueResponse($issue);
+    }
+
+    $issue_keys = PhabricatorSetupCheck::getUnignoredIssueKeys($issues);
+
+    PhabricatorSetupCheck::setOpenSetupIssueKeys(
+      $issue_keys,
+      $update_database = true);
+
+    $this->issues = $issues;
+
+    return null;
+  }
+
+}