diff --git a/backend/src/api/bitcoin/bitcoin.routes.ts b/backend/src/api/bitcoin/bitcoin.routes.ts
index 18d688e9b..16533b68c 100644
--- a/backend/src/api/bitcoin/bitcoin.routes.ts
+++ b/backend/src/api/bitcoin/bitcoin.routes.ts
@@ -130,8 +130,9 @@ class BitcoinRoutes {
 
   private getInitData(req: Request, res: Response) {
     try {
-      const result = websocketHandler.getInitData();
-      res.json(result);
+      const result = websocketHandler.getSerializedInitData();
+      res.set('Content-Type', 'application/json');
+      res.send(result);
     } catch (e) {
       res.status(500).send(e instanceof Error ? e.message : e);
     }
diff --git a/backend/src/api/websocket-handler.ts b/backend/src/api/websocket-handler.ts
index bc0fb8ea5..3fa7006fb 100644
--- a/backend/src/api/websocket-handler.ts
+++ b/backend/src/api/websocket-handler.ts
@@ -30,6 +30,9 @@ class WebsocketHandler {
   private numConnected = 0;
   private numDisconnected = 0;
 
+  private initData: { [key: string]: string } = {};
+  private serializedInitData: string = '{}';
+
   constructor() { }
 
   setWebsocketServer(wss: WebSocket.Server) {
@@ -38,6 +41,41 @@ class WebsocketHandler {
 
   setExtraInitProperties(property: string, value: any) {
     this.extraInitProperties[property] = value;
+    this.setInitDataFields(this.extraInitProperties);
+  }
+
+  private setInitDataFields(data: { [property: string]: any }): void {
+    for (const property of Object.keys(data)) {
+      if (data[property] != null) {
+        this.initData[property] = JSON.stringify(data[property]);
+      } else {
+        delete this.initData[property];
+      }
+    }
+    this.serializedInitData = '{'
+      + Object.keys(this.initData).map(key => `"${key}": ${this.initData[key]}`).join(', ')
+      + '}';
+  }
+
+  private updateInitData(): void {
+    const _blocks = blocks.getBlocks().slice(-config.MEMPOOL.INITIAL_BLOCKS_AMOUNT);
+    const da = difficultyAdjustment.getDifficultyAdjustment();
+    this.setInitDataFields({
+      'mempoolInfo': memPool.getMempoolInfo(),
+      'vBytesPerSecond': memPool.getVBytesPerSecond(),
+      'blocks': _blocks,
+      'conversions': priceUpdater.getLatestPrices(),
+      'mempool-blocks': mempoolBlocks.getMempoolBlocks(),
+      'transactions': memPool.getLatestTransactions(),
+      'backendInfo': backendInfo.getBackendInfo(),
+      'loadingIndicators': loadingIndicators.getLoadingIndicators(),
+      'da': da?.previousTime ? da : undefined,
+      'fees': feeApi.getRecommendedFee(),
+    });
+  }
+
+  public getSerializedInitData(): string {
+    return this.serializedInitData;
   }
 
   setupConnectionHandling() {
@@ -157,11 +195,13 @@ class WebsocketHandler {
           }
 
           if (parsedMessage.action === 'init') {
-            const _blocks = blocks.getBlocks().slice(-config.MEMPOOL.INITIAL_BLOCKS_AMOUNT);
-            if (!_blocks) {
+            if (!this.initData['blocks']?.length || !this.initData['da']) {
+              this.updateInitData();
+            }
+            if (!this.initData['blocks']?.length) {
               return;
             }
-            client.send(JSON.stringify(this.getInitData(_blocks)));
+            client.send(this.serializedInitData);
           }
 
           if (parsedMessage.action === 'ping') {
@@ -210,11 +250,14 @@ class WebsocketHandler {
       throw new Error('WebSocket.Server is not set');
     }
 
+    this.setInitDataFields({ 'loadingIndicators': indicators });
+
+    const response = JSON.stringify({ loadingIndicators: indicators });
     this.wss.clients.forEach((client) => {
       if (client.readyState !== WebSocket.OPEN) {
         return;
       }
-      client.send(JSON.stringify({ loadingIndicators: indicators }));
+      client.send(response);
     });
   }
 
@@ -223,34 +266,17 @@ class WebsocketHandler {
       throw new Error('WebSocket.Server is not set');
     }
 
+    this.setInitDataFields({ 'conversions': conversionRates });
+
+    const response = JSON.stringify({ conversions: conversionRates });
     this.wss.clients.forEach((client) => {
       if (client.readyState !== WebSocket.OPEN) {
         return;
       }
-      client.send(JSON.stringify({ conversions: conversionRates }));
+      client.send(response);
     });
   }
 
-  getInitData(_blocks?: BlockExtended[]) {
-    if (!_blocks) {
-      _blocks = blocks.getBlocks().slice(-config.MEMPOOL.INITIAL_BLOCKS_AMOUNT);
-    }
-    const da = difficultyAdjustment.getDifficultyAdjustment();
-    return {
-      'mempoolInfo': memPool.getMempoolInfo(),
-      'vBytesPerSecond': memPool.getVBytesPerSecond(),
-      'blocks': _blocks,
-      'conversions': priceUpdater.getLatestPrices(),
-      'mempool-blocks': mempoolBlocks.getMempoolBlocks(),
-      'transactions': memPool.getLatestTransactions(),
-      'backendInfo': backendInfo.getBackendInfo(),
-      'loadingIndicators': loadingIndicators.getLoadingIndicators(),
-      'da': da?.previousTime ? da : undefined,
-      'fees': feeApi.getRecommendedFee(),
-      ...this.extraInitProperties
-    };
-  }
-
   handleNewStatistic(stats: OptimizedStatistic) {
     if (!this.wss) {
       throw new Error('WebSocket.Server is not set');
@@ -258,6 +284,10 @@ class WebsocketHandler {
 
     this.printLogs();
 
+    const response = JSON.stringify({
+      'live-2h-chart': stats
+    });
+
     this.wss.clients.forEach((client) => {
       if (client.readyState !== WebSocket.OPEN) {
         return;
@@ -267,9 +297,7 @@ class WebsocketHandler {
         return;
       }
 
-      client.send(JSON.stringify({
-        'live-2h-chart': stats
-      }));
+      client.send(response);
     });
   }
 
@@ -306,6 +334,43 @@ class WebsocketHandler {
     }
     const recommendedFees = feeApi.getRecommendedFee();
 
+    // update init data
+    this.updateInitData();
+
+    // cache serialized objects to avoid stringify-ing the same thing for every client
+    const responseCache = { ...this.initData };
+    function getCachedResponse(key: string,  data): string {
+      if (!responseCache[key]) {
+        responseCache[key] = JSON.stringify(data);
+      }
+      return responseCache[key];
+    }
+
+    // pre-compute new tracked outspends
+    const outspendCache: { [txid: string]: { [vout: number]: { vin: number, txid: string } } } = {};
+    const trackedTxs = new Set<string>();
+    this.wss.clients.forEach((client) => {
+      if (client['track-tx']) {
+        trackedTxs.add(client['track-tx']);
+      }
+    });
+    if (trackedTxs.size > 0) {
+      for (const tx of newTransactions) {
+        for (let i = 0; i < tx.vin.length; i++) {
+          const vin = tx.vin[i];
+          if (trackedTxs.has(vin.txid)) {
+            if (!outspendCache[vin.txid]) {
+              outspendCache[vin.txid] = { [vin.vout]: { vin: i, txid: tx.txid }};
+            } else {
+              outspendCache[vin.txid][vin.vout] = { vin: i, txid: tx.txid };
+            }
+          }
+        }
+      }
+    }
+
+    const latestTransactions = newTransactions.slice(0, 6).map((tx) => Common.stripTransaction(tx));
+
     this.wss.clients.forEach(async (client) => {
       if (client.readyState !== WebSocket.OPEN) {
         return;
@@ -314,17 +379,17 @@ class WebsocketHandler {
       const response = {};
 
       if (client['want-stats']) {
-        response['mempoolInfo'] = mempoolInfo;
-        response['vBytesPerSecond'] = vBytesPerSecond;
-        response['transactions'] = newTransactions.slice(0, 6).map((tx) => Common.stripTransaction(tx));
+        response['mempoolInfo'] = getCachedResponse('mempoolInfo', mempoolInfo);
+        response['vBytesPerSecond'] = getCachedResponse('vBytesPerSecond', vBytesPerSecond);
+        response['transactions'] = getCachedResponse('transactions', latestTransactions);
         if (da?.previousTime) {
-          response['da'] = da;
+          response['da'] = getCachedResponse('da', da);
         }
-        response['fees'] = recommendedFees;
+        response['fees'] = getCachedResponse('fees', recommendedFees);
       }
 
       if (client['want-mempool-blocks']) {
-        response['mempool-blocks'] = mBlocks;
+        response['mempool-blocks'] = getCachedResponse('mempool-blocks', mBlocks);
       }
 
       if (client['track-mempool-tx']) {
@@ -333,12 +398,12 @@ class WebsocketHandler {
           if (config.MEMPOOL.BACKEND !== 'esplora') {
             try {
               const fullTx = await transactionUtils.$getTransactionExtended(tx.txid, true);
-              response['tx'] = fullTx;
+              response['tx'] = JSON.stringify(fullTx);
             } catch (e) {
               logger.debug('Error finding transaction in mempool: ' + (e instanceof Error ? e.message : e));
             }
           } else {
-            response['tx'] = tx;
+            response['tx'] = JSON.stringify(tx);
           }
           client['track-mempool-tx'] = null;
         }
@@ -378,7 +443,7 @@ class WebsocketHandler {
         }
 
         if (foundTransactions.length) {
-          response['address-transactions'] = foundTransactions;
+          response['address-transactions'] = JSON.stringify(foundTransactions);
         }
       }
 
@@ -407,65 +472,60 @@ class WebsocketHandler {
         });
 
         if (foundTransactions.length) {
-          response['address-transactions'] = foundTransactions;
+          response['address-transactions'] = JSON.stringify(foundTransactions);
         }
       }
 
       if (client['track-tx']) {
         const trackTxid = client['track-tx'];
-        const outspends: object = {};
-        newTransactions.forEach((tx) => tx.vin.forEach((vin, i) => {
-          if (vin.txid === trackTxid) {
-            outspends[vin.vout] = {
-              vin: i,
-              txid: tx.txid,
-            };
-          }
-        }));
+        const outspends = outspendCache[trackTxid];
 
-        if (Object.keys(outspends).length) {
-          response['utxoSpent'] = outspends;
+        if (outspends && Object.keys(outspends).length) {
+          response['utxoSpent'] = JSON.stringify(outspends);
         }
 
         const rbfReplacedBy = rbfCache.getReplacedBy(client['track-tx']);
         if (rbfReplacedBy) {
-          response['rbfTransaction'] = {
+          response['rbfTransaction'] = JSON.stringify({
             txid: rbfReplacedBy,
-          }
+          })
         }
 
         const rbfChange = rbfChanges.map[client['track-tx']];
         if (rbfChange) {
-          response['rbfInfo'] = rbfChanges.trees[rbfChange];
+          response['rbfInfo'] = JSON.stringify(rbfChanges.trees[rbfChange]);
         }
 
         const mempoolTx = newMempool[trackTxid];
         if (mempoolTx && mempoolTx.position) {
-          response['txPosition'] = {
+          response['txPosition'] = JSON.stringify({
             txid: trackTxid,
             position: mempoolTx.position,
-          };
+          });
         }
       }
 
       if (client['track-mempool-block'] >= 0) {
         const index = client['track-mempool-block'];
         if (mBlockDeltas[index]) {
-          response['projected-block-transactions'] = {
+          response['projected-block-transactions'] = getCachedResponse(`projected-block-transactions-${index}`, {
             index: index,
             delta: mBlockDeltas[index],
-          };
+          });
         }
       }
 
       if (client['track-rbf'] === 'all' && rbfReplacements) {
-        response['rbfLatest'] = rbfReplacements;
+        response['rbfLatest'] = getCachedResponse('rbfLatest', rbfReplacements);
       } else if (client['track-rbf'] === 'fullRbf' && fullRbfReplacements) {
-        response['rbfLatest'] = fullRbfReplacements;
+        response['rbfLatest'] = getCachedResponse('fullrbfLatest', fullRbfReplacements);
       }
 
       if (Object.keys(response).length) {
-        client.send(JSON.stringify(response));
+        const serializedResponse = '{'
+          + Object.keys(response).map(key => `"${key}": ${response[key]}`).join(', ')
+          + '}';
+        client.send(serializedResponse);
       }
     });
   }
@@ -556,6 +616,19 @@ class WebsocketHandler {
     const da = difficultyAdjustment.getDifficultyAdjustment();
     const fees = feeApi.getRecommendedFee();
 
+    // update init data
+    this.updateInitData();
+
+    const responseCache = { ...this.initData };
+    function getCachedResponse(key, data): string {
+      if (!responseCache[key]) {
+        responseCache[key] = JSON.stringify(data);
+      }
+      return responseCache[key];
+    }
+
+    const mempoolInfo = memPool.getMempoolInfo();
+
     this.wss.clients.forEach((client) => {
       if (client.readyState !== WebSocket.OPEN) {
         return;
@@ -565,28 +638,27 @@ class WebsocketHandler {
         return;
       }
 
-      const response = {
-        'block': block,
-        'mempoolInfo': memPool.getMempoolInfo(),
-        'da': da?.previousTime ? da : undefined,
-        'fees': fees,
-      };
+      const response = {};
+      response['block'] = getCachedResponse('block', block);
+      response['mempoolInfo'] = getCachedResponse('mempoolInfo', mempoolInfo);
+      response['da'] = getCachedResponse('da', da?.previousTime ? da : undefined);
+      response['fees'] = getCachedResponse('fees', fees);
 
       if (mBlocks && client['want-mempool-blocks']) {
-        response['mempool-blocks'] = mBlocks;
+        response['mempool-blocks'] = getCachedResponse('mempool-blocks', mBlocks);
       }
 
       if (client['track-tx']) {
         const trackTxid = client['track-tx'];
         if (txIds.indexOf(trackTxid) > -1) {
-          response['txConfirmed'] = true;
+          response['txConfirmed'] = 'true';
         } else {
           const mempoolTx = _memPool[trackTxid];
           if (mempoolTx && mempoolTx.position) {
-            response['txPosition'] = {
+            response['txPosition'] = JSON.stringify({
               txid: trackTxid,
               position: mempoolTx.position,
-            };
+            });
           }
         }
       }
@@ -614,7 +686,7 @@ class WebsocketHandler {
             };
           });
 
-          response['block-transactions'] = foundTransactions;
+          response['block-transactions'] = JSON.stringify(foundTransactions);
         }
       }
 
@@ -651,21 +723,24 @@ class WebsocketHandler {
             };
           });
 
-          response['block-transactions'] = foundTransactions;
+          response['block-transactions'] = JSON.stringify(foundTransactions);
         }
       }
 
       if (client['track-mempool-block'] >= 0) {
         const index = client['track-mempool-block'];
         if (mBlockDeltas && mBlockDeltas[index]) {
-          response['projected-block-transactions'] = {
+          response['projected-block-transactions'] = getCachedResponse(`projected-block-transactions-${index}`, {
             index: index,
             delta: mBlockDeltas[index],
-          };
+          });
         }
       }
 
-      client.send(JSON.stringify(response));
+      const serializedResponse = '{'
+        + Object.keys(response).map(key => `"${key}": ${response[key]}`).join(', ')
+        + '}';
+      client.send(serializedResponse);
     });
   }