diff --git a/src/app.js b/src/app.js
index c6afc27f8..2dad38c7d 100644
--- a/src/app.js
+++ b/src/app.js
@@ -43,7 +43,7 @@ require('./routes/custom.js').register(app);
 require('./routes/error_handlers.js').register(app);
 
 // triggers sync timer
-require('./services/sync.js');
+require('./services/sync');
 
 // triggers backup timer
 require('./services/backup');
diff --git a/src/routes/api/script.js b/src/routes/api/script.js
index 2dac2ca64..f7903f411 100644
--- a/src/routes/api/script.js
+++ b/src/routes/api/script.js
@@ -3,7 +3,7 @@
 const scriptService = require('../../services/script.js');
 const attributeService = require('../../services/attributes');
 const becca = require('../../becca/becca');
-const syncService = require('../../services/sync.js');
+const syncService = require('../../services/sync');
 const sql = require('../../services/sql');
 
 // The async/await here is very confusing, because the body.script may, but may not be async. If it is async, then we
diff --git a/src/routes/api/sync.js b/src/routes/api/sync.js
index 0d68827e1..c1939552e 100644
--- a/src/routes/api/sync.js
+++ b/src/routes/api/sync.js
@@ -1,6 +1,6 @@
 "use strict";
 
-const syncService = require('../../services/sync.js');
+const syncService = require('../../services/sync');
 const syncUpdateService = require('../../services/sync_update');
 const entityChangesService = require('../../services/entity_changes');
 const sql = require('../../services/sql');
diff --git a/src/routes/routes.js b/src/routes/routes.js
index 7c5ea7e0a..0b906f9f1 100644
--- a/src/routes/routes.js
+++ b/src/routes/routes.js
@@ -32,7 +32,7 @@ const revisionsApiRoute = require('./api/revisions');
 const recentChangesApiRoute = require('./api/recent_changes.js');
 const optionsApiRoute = require('./api/options.js');
 const passwordApiRoute = require('./api/password');
-const syncApiRoute = require('./api/sync.js');
+const syncApiRoute = require('./api/sync');
 const loginApiRoute = require('./api/login.js');
 const recentNotesRoute = require('./api/recent_notes.js');
 const appInfoRoute = require('./api/app_info');
diff --git a/src/services/entity_changes_interface.ts b/src/services/entity_changes_interface.ts
index 745a8a8fa..a0e6bb4bc 100644
--- a/src/services/entity_changes_interface.ts
+++ b/src/services/entity_changes_interface.ts
@@ -12,4 +12,14 @@ export interface EntityChange {
 	componentId?: string | null;
 	changeId?: string | null;
 	instanceId?: string | null;
-}
\ No newline at end of file
+}
+
+export interface EntityRow {
+	isDeleted?: boolean;
+	content?: Buffer | string;
+}
+
+export interface EntityChangeRecord {
+    entityChange: EntityChange;
+    entity?: EntityRow;
+}
diff --git a/src/services/request.ts b/src/services/request.ts
index 47be2d2ef..9922e4b2d 100644
--- a/src/services/request.ts
+++ b/src/services/request.ts
@@ -4,29 +4,11 @@ import utils = require('./utils');
 import log = require('./log');
 import url = require('url');
 import syncOptions = require('./sync_options');
+import { ExecOpts } from './request_interface';
 
 // this service provides abstraction over node's HTTP/HTTPS and electron net.client APIs
 // this allows supporting system proxy
 
-interface ExecOpts {
-    proxy: "noproxy" | null;
-    method: string;
-    url: string;
-    paging?: {
-        pageCount: number;
-        pageIndex: number;
-        requestId: string;
-    };
-    cookieJar?: {
-        header?: string;
-    };
-    auth?: {
-        password?: string;
-    },
-    timeout: number;
-    body: string;
-}
-
 interface ClientOpts {
     method: string;
     url: string;
diff --git a/src/services/request_interface.ts b/src/services/request_interface.ts
new file mode 100644
index 000000000..4ba1da0a7
--- /dev/null
+++ b/src/services/request_interface.ts
@@ -0,0 +1,20 @@
+export interface CookieJar {
+    header?: string;
+}
+
+export interface ExecOpts {
+    proxy: "noproxy" | null;
+    method: string;
+    url: string;
+    paging?: {
+        pageCount: number;
+        pageIndex: number;
+        requestId: string;
+    };
+    cookieJar?: CookieJar;
+    auth?: {
+        password?: string;
+    },
+    timeout: number;
+    body: string;
+}
\ No newline at end of file
diff --git a/src/services/setup.js b/src/services/setup.js
index 55e559e87..9c5d0c0c4 100644
--- a/src/services/setup.js
+++ b/src/services/setup.js
@@ -1,4 +1,4 @@
-const syncService = require('./sync.js');
+const syncService = require('./sync');
 const log = require('./log');
 const sqlInit = require('./sql_init');
 const optionService = require('./options');
diff --git a/src/services/sync.js b/src/services/sync.ts
similarity index 75%
rename from src/services/sync.js
rename to src/services/sync.ts
index a935e1de8..da559e36a 100644
--- a/src/services/sync.js
+++ b/src/services/sync.ts
@@ -1,27 +1,50 @@
 "use strict";
 
-const log = require('./log');
-const sql = require('./sql');
-const optionService = require('./options');
-const utils = require('./utils');
-const instanceId = require('./instance_id');
-const dateUtils = require('./date_utils');
-const syncUpdateService = require('./sync_update');
-const contentHashService = require('./content_hash');
-const appInfo = require('./app_info');
-const syncOptions = require('./sync_options');
-const syncMutexService = require('./sync_mutex');
-const cls = require('./cls');
-const request = require('./request');
-const ws = require('./ws');
-const entityChangesService = require('./entity_changes');
-const entityConstructor = require('../becca/entity_constructor');
-const becca = require('../becca/becca');
+import log = require('./log');
+import sql = require('./sql');
+import optionService = require('./options');
+import utils = require('./utils');
+import instanceId = require('./instance_id');
+import dateUtils = require('./date_utils');
+import syncUpdateService = require('./sync_update');
+import contentHashService = require('./content_hash');
+import appInfo = require('./app_info');
+import syncOptions = require('./sync_options');
+import syncMutexService = require('./sync_mutex');
+import cls = require('./cls');
+import request = require('./request');
+import ws = require('./ws');
+import entityChangesService = require('./entity_changes');
+import entityConstructor = require('../becca/entity_constructor');
+import becca = require('../becca/becca');
+import { EntityChange, EntityChangeRecord, EntityRow } from './entity_changes_interface';
+import { CookieJar, ExecOpts } from './request_interface';
 
 let proxyToggle = true;
 
 let outstandingPullCount = 0;
 
+interface CheckResponse {
+    maxEntityChangeId: number;
+    entityHashes: Record<string, Record<string, string>>
+}
+
+interface SyncResponse {
+    instanceId: string;
+    maxEntityChangeId: number;
+}
+
+interface ChangesResponse {
+    entityChanges: EntityChangeRecord[];
+    lastEntityChangeId: number;
+    outstandingPullCount: number;
+}
+
+interface SyncContext {
+    cookieJar: CookieJar;
+    instanceId?: string;
+}
+
 async function sync() {
     try {
         return await syncMutexService.doExclusively(async () => {
@@ -53,7 +76,7 @@ async function sync() {
             };
         });
     }
-    catch (e) {
+    catch (e: any) {
         // we're dynamically switching whether we're using proxy or not based on whether we encountered error with the current method
         proxyToggle = !proxyToggle;
 
@@ -93,19 +116,23 @@ async function login() {
     return await doLogin();
 }
 
-async function doLogin() {
+async function doLogin(): Promise<SyncContext> {
     const timestamp = dateUtils.utcNowDateTime();
 
     const documentSecret = optionService.getOption('documentSecret');
     const hash = utils.hmac(documentSecret, timestamp);
 
-    const syncContext = { cookieJar: {} };
-    const resp = await syncRequest(syncContext, 'POST', '/api/login/sync', {
+    const syncContext: SyncContext = { cookieJar: {} };
+    const resp = await syncRequest<SyncResponse>(syncContext, 'POST', '/api/login/sync', {
         timestamp: timestamp,
         syncVersion: appInfo.syncVersion,
         hash: hash
     });
 
+    if (!resp) {
+        throw new Error("Got no response.");
+    }
+
     if (resp.instanceId === instanceId) {
         throw new Error(`Sync server has instance ID '${resp.instanceId}' which is also local. This usually happens when the sync client is (mis)configured to sync with itself (URL points back to client) instead of the correct sync server.`);
     }
@@ -125,7 +152,7 @@ async function doLogin() {
     return syncContext;
 }
 
-async function pullChanges(syncContext) {
+async function pullChanges(syncContext: SyncContext) {    
     while (true) {
         const lastSyncedPull = getLastSyncedPull();
         const logMarkerId = utils.randomString(10); // to easily pair sync events between client and server logs
@@ -133,7 +160,10 @@ async function pullChanges(syncContext) {
 
         const startDate = Date.now();
 
-        const resp = await syncRequest(syncContext, 'GET', changesUri);
+        const resp = await syncRequest<ChangesResponse>(syncContext, 'GET', changesUri);
+        if (!resp) {
+            throw new Error("Request failed.");
+        }
         const {entityChanges, lastEntityChangeId} = resp;
 
         outstandingPullCount = resp.outstandingPullCount;
@@ -141,7 +171,9 @@ async function pullChanges(syncContext) {
         const pulledDate = Date.now();
 
         sql.transactional(() => {
-            syncUpdateService.updateEntities(entityChanges, syncContext.instanceId);
+            if (syncContext.instanceId) {
+                syncUpdateService.updateEntities(entityChanges, syncContext.instanceId);
+            }
 
             if (lastSyncedPull !== lastEntityChangeId) {
                 setLastSyncedPull(lastEntityChangeId);
@@ -156,7 +188,7 @@ async function pullChanges(syncContext) {
 
                 log.info(`Sync ${logMarkerId}: Pulled ${entityChanges.length} changes in ${sizeInKb} KB, starting at entityChangeId=${lastSyncedPull} in ${pulledDate - startDate}ms and applied them in ${Date.now() - pulledDate}ms, ${outstandingPullCount} outstanding pulls`);
             }
-            catch (e) {
+            catch (e: any) {
                 log.error(`Error occurred ${e.message} ${e.stack}`);
             }
         }
@@ -165,11 +197,11 @@ async function pullChanges(syncContext) {
     log.info("Finished pull");
 }
 
-async function pushChanges(syncContext) {
-    let lastSyncedPush = getLastSyncedPush();
+async function pushChanges(syncContext: SyncContext) {
+    let lastSyncedPush: number | null | undefined = getLastSyncedPush();
 
     while (true) {
-        const entityChanges = sql.getRows('SELECT * FROM entity_changes WHERE isSynced = 1 AND id > ? LIMIT 1000', [lastSyncedPush]);
+        const entityChanges = sql.getRows<EntityChange>('SELECT * FROM entity_changes WHERE isSynced = 1 AND id > ? LIMIT 1000', [lastSyncedPush]);
 
         if (entityChanges.length === 0) {
             log.info("Nothing to push");
@@ -190,7 +222,7 @@ async function pushChanges(syncContext) {
             }
         });
 
-        if (filteredEntityChanges.length === 0) {
+        if (filteredEntityChanges.length === 0 && lastSyncedPush) {
             // there still might be more sync changes (because of batch limit), just all the current batch
             // has been filtered out
             setLastSyncedPush(lastSyncedPush);
@@ -214,16 +246,22 @@ async function pushChanges(syncContext) {
 
         lastSyncedPush = entityChangesRecords[entityChangesRecords.length - 1].entityChange.id;
 
-        setLastSyncedPush(lastSyncedPush);
+        if (lastSyncedPush) {
+            setLastSyncedPush(lastSyncedPush);
+        }
     }
 }
 
-async function syncFinished(syncContext) {
+async function syncFinished(syncContext: SyncContext) {
     await syncRequest(syncContext, 'POST', '/api/sync/finished');
 }
 
-async function checkContentHash(syncContext) {
-    const resp = await syncRequest(syncContext, 'GET', '/api/sync/check');
+async function checkContentHash(syncContext: SyncContext) {
+    const resp = await syncRequest<CheckResponse>(syncContext, 'GET', '/api/sync/check');
+    if (!resp) {
+        throw new Error("Got no response.");
+    }
+
     const lastSyncedPullId = getLastSyncedPull();
 
     if (lastSyncedPullId < resp.maxEntityChangeId) {
@@ -261,8 +299,12 @@ async function checkContentHash(syncContext) {
 
 const PAGE_SIZE = 1000000;
 
-async function syncRequest(syncContext, method, requestPath, body) {
-    body = body ? JSON.stringify(body) : '';
+interface SyncContext {
+    cookieJar: CookieJar
+}
+
+async function syncRequest<T extends {}>(syncContext: SyncContext, method: string, requestPath: string, _body?: {}) {
+    const body = _body ? JSON.stringify(_body) : '';
 
     const timeout = syncOptions.getSyncTimeout();
 
@@ -272,7 +314,7 @@ async function syncRequest(syncContext, method, requestPath, body) {
     const pageCount = Math.max(1, Math.ceil(body.length / PAGE_SIZE));
 
     for (let pageIndex = 0; pageIndex < pageCount; pageIndex++) {
-        const opts = {
+        const opts: ExecOpts = {
             method,
             url: syncOptions.getSyncServerHost() + requestPath,
             cookieJar: syncContext.cookieJar,
@@ -286,13 +328,13 @@ async function syncRequest(syncContext, method, requestPath, body) {
             proxy: proxyToggle ? syncOptions.getSyncProxy() : null
         };
 
-        response = await utils.timeLimit(request.exec(opts), timeout);
+        response = await utils.timeLimit(request.exec(opts), timeout) as T;
     }
 
     return response;
 }
 
-function getEntityChangeRow(entityChange) {
+function getEntityChangeRow(entityChange: EntityChange) {
     const {entityName, entityId} = entityChange;
 
     if (entityName === 'note_reordering') {
@@ -305,7 +347,7 @@ function getEntityChangeRow(entityChange) {
             throw new Error(`Unknown entity for entity change ${JSON.stringify(entityChange)}`);
         }
 
-        const entityRow = sql.getRow(`SELECT * FROM ${entityName} WHERE ${primaryKey} = ?`, [entityId]);
+        const entityRow = sql.getRow<EntityRow>(`SELECT * FROM ${entityName} WHERE ${primaryKey} = ?`, [entityId]);
 
         if (!entityRow) {
             log.error(`Cannot find entity for entity change ${JSON.stringify(entityChange)}`);
@@ -317,15 +359,17 @@ function getEntityChangeRow(entityChange) {
                 entityRow.content = Buffer.from(entityRow.content, 'utf-8');
             }
 
-            entityRow.content = entityRow.content.toString("base64");
+            if (entityRow.content) {
+                entityRow.content = entityRow.content.toString("base64");
+            }
         }
 
         return entityRow;
     }
 }
 
-function getEntityChangeRecords(entityChanges) {
-    const records = [];
+function getEntityChangeRecords(entityChanges: EntityChange[]) {
+    const records: EntityChangeRecord[] = [];
     let length = 0;
 
     for (const entityChange of entityChanges) {
@@ -340,7 +384,7 @@ function getEntityChangeRecords(entityChanges) {
             continue;
         }
 
-        const record = { entityChange, entity };
+        const record: EntityChangeRecord = { entityChange, entity };
 
         records.push(record);
 
@@ -359,7 +403,7 @@ function getLastSyncedPull() {
     return parseInt(optionService.getOption('lastSyncedPull'));
 }
 
-function setLastSyncedPull(entityChangeId) {
+function setLastSyncedPull(entityChangeId: number) {
     const lastSyncedPullOption = becca.getOption('lastSyncedPull');
 
     if (lastSyncedPullOption) { // might be null in initial sync when becca is not loaded
@@ -378,7 +422,7 @@ function getLastSyncedPush() {
     return lastSyncedPush;
 }
 
-function setLastSyncedPush(entityChangeId) {
+function setLastSyncedPush(entityChangeId: number) {
     ws.setLastSyncedPush(entityChangeId);
 
     const lastSyncedPushOption = becca.getOption('lastSyncedPush');
@@ -409,7 +453,7 @@ require('../becca/becca_loader').beccaLoaded.then(() => {
     getLastSyncedPush();
 });
 
-module.exports = {
+export = {
     sync,
     login,
     getEntityChangeRecords,
diff --git a/src/services/sync_update.ts b/src/services/sync_update.ts
index bed9dcaf6..888947b8b 100644
--- a/src/services/sync_update.ts
+++ b/src/services/sync_update.ts
@@ -4,17 +4,7 @@ import entityChangesService = require('./entity_changes');
 import eventService = require('./events');
 import entityConstructor = require('../becca/entity_constructor');
 import ws = require('./ws');
-import { EntityChange } from './entity_changes_interface';
-
-interface EntityRow {
-    isDeleted?: boolean;
-    content: Buffer | string;
-}
-
-interface EntityChangeInput {
-    entityChange: EntityChange;
-    entity: EntityRow;
-}
+import { EntityChange, EntityChangeRecord, EntityRow } from './entity_changes_interface';
 
 interface UpdateContext {
     alreadyErased: number;
@@ -22,7 +12,7 @@ interface UpdateContext {
     updated: Record<string, string[]>
 }
 
-function updateEntities(entityChanges: EntityChangeInput[], instanceId: string) {
+function updateEntities(entityChanges: EntityChangeRecord[], instanceId: string) {
     if (entityChanges.length === 0) {
         return;
     }
@@ -51,7 +41,9 @@ function updateEntities(entityChanges: EntityChangeInput[], instanceId: string)
             atLeastOnePullApplied = true;
         }
 
-        updateEntity(entityChange, entity, instanceId, updateContext);
+        if (entity) {
+            updateEntity(entityChange, entity, instanceId, updateContext);
+        }
     }
 
     logUpdateContext(updateContext);
diff --git a/src/services/utils.ts b/src/services/utils.ts
index 4cbb96d2f..852b9a1df 100644
--- a/src/services/utils.ts
+++ b/src/services/utils.ts
@@ -238,7 +238,7 @@ function getNoteTitle(filePath: string, replaceUnderscoresWithSpaces: boolean, n
     }
 }
 
-function timeLimit<T>(promise: Promise<T>, limitMs: number, errorMessage: string): Promise<T> {
+function timeLimit<T>(promise: Promise<T>, limitMs: number, errorMessage?: string): Promise<T> {
     if (!promise || !promise.then) { // it's not actually a promise
         return promise;
     }