diff --git a/lib/socket/api-request-handler.react.js b/lib/socket/api-request-handler.react.js
--- a/lib/socket/api-request-handler.react.js
+++ b/lib/socket/api-request-handler.react.js
@@ -26,7 +26,7 @@
   +connection: ConnectionInfo,
 };
 class APIRequestHandler extends React.PureComponent<Props> {
-  static isConnected(props: Props, request?: APIRequest) {
+  static isConnected(props: Props, request?: APIRequest): boolean {
     const { inflightRequests, connection } = props;
     if (!inflightRequests) {
       return false;
@@ -44,11 +44,11 @@
     // will be a great way to rewrite them to be related but still separated.
     return (
       connection.status === 'connected' ||
-      (request && request.endpoint === 'update_activity')
+      request?.endpoint === 'update_activity'
     );
   }
 
-  get registeredResponseFetcher() {
+  get registeredResponseFetcher(): ?(request: APIRequest) => Promise<mixed> {
     return APIRequestHandler.isConnected(this.props)
       ? this.fetchResponse
       : null;
@@ -70,11 +70,11 @@
     }
   }
 
-  render() {
+  render(): React.Node {
     return null;
   }
 
-  fetchResponse = async (request: APIRequest): Promise<Object> => {
+  fetchResponse = async (request: APIRequest): Promise<mixed> => {
     if (!APIRequestHandler.isConnected(this.props, request)) {
       throw new SocketOffline('socket_offline');
     }
diff --git a/lib/socket/calendar-query-handler.react.js b/lib/socket/calendar-query-handler.react.js
--- a/lib/socket/calendar-query-handler.react.js
+++ b/lib/socket/calendar-query-handler.react.js
@@ -82,11 +82,11 @@
     }
   }
 
-  render() {
+  render(): React.Node {
     return null;
   }
 
-  get isExpired() {
+  get isExpired(): boolean {
     const timeUntilExpiration = timeUntilCalendarRangeExpiration(
       this.props.lastUserInteractionCalendar,
     );
@@ -97,7 +97,7 @@
     );
   }
 
-  get shouldUpdateCalendarQuery() {
+  get shouldUpdateCalendarQuery(): boolean {
     if (this.props.connection.status !== 'connected' || this.props.frozen) {
       return false;
     }
diff --git a/lib/socket/inflight-requests.js b/lib/socket/inflight-requests.js
--- a/lib/socket/inflight-requests.js
+++ b/lib/socket/inflight-requests.js
@@ -104,11 +104,9 @@
         };
       }
     });
-    invariant(
-      inflightRequest,
-      `${expectedType} is an invalid server response type`,
-    );
-    this.data.push(inflightRequest);
+    const request = inflightRequest;
+    invariant(request, `${expectedType} is an invalid server response type`);
+    this.data.push(request);
 
     // We create this object so we can pass it by reference to the timeout
     // function below. That function will avoid setting this request as late if
@@ -124,12 +122,12 @@
       if (requestResult.lateResponse) {
         this.setLateResponse(messageID, false);
       }
-      this.clearRequest(inflightRequest);
+      this.clearRequest(request);
       // Flow is unable to narrow the return type based on the expectedType
       return (response: any);
     } catch (e) {
       requestResult.concluded = true;
-      this.clearRequest(inflightRequest);
+      this.clearRequest(request);
       if (e instanceof SocketTimeout) {
         this.rejectAll(new Error('socket closed due to timeout'));
         this.timeoutCallback();
@@ -144,7 +142,7 @@
     messageID: number,
     expectedType: ServerSocketMessageType,
     requestResult: { concluded: boolean, lateResponse: boolean },
-  ) {
+  ): Promise<void> {
     await sleep(clientRequestVisualTimeout);
     if (requestResult.concluded) {
       // We're just doing this to bail out. If requestResult.concluded we can
diff --git a/lib/socket/report-handler.react.js b/lib/socket/report-handler.react.js
--- a/lib/socket/report-handler.react.js
+++ b/lib/socket/report-handler.react.js
@@ -52,7 +52,7 @@
     }
   }
 
-  render() {
+  render(): React.Node {
     return null;
   }
 
@@ -66,9 +66,11 @@
     );
   }
 
-  async sendReports(reports: $ReadOnlyArray<ClientReportCreationRequest>) {
+  async sendReports(
+    reports: $ReadOnlyArray<ClientReportCreationRequest>,
+  ): Promise<ClearDeliveredReportsPayload> {
     await sendReports(reports);
-    return ({ reports }: ClearDeliveredReportsPayload);
+    return { reports };
   }
 }
 
diff --git a/lib/socket/request-response-handler.react.js b/lib/socket/request-response-handler.react.js
--- a/lib/socket/request-response-handler.react.js
+++ b/lib/socket/request-response-handler.react.js
@@ -48,7 +48,7 @@
     this.props.removeListener(this.onMessage);
   }
 
-  render() {
+  render(): React.Node {
     return null;
   }