diff --git a/apps/ui/js/usage.js b/apps/ui/js/usage.js
index 94d34c8..35bd7c2 100644
--- a/apps/ui/js/usage.js
+++ b/apps/ui/js/usage.js
@@ -3,6 +3,12 @@ document.addEventListener('DOMContentLoaded', function () {
     period: '7d',
     workspaceId: null,
     usage: null,
+    derived: {
+      localizedOperations: [],
+      normalizedTimeline: [],
+      timelineMaxValue: 0,
+      totalCalls: 0,
+    },
     loading: false,
     loadError: '',
   };
@@ -203,6 +209,29 @@ document.addEventListener('DOMContentLoaded', function () {
     return normalized;
   }
 
+  function recomputeDerivedState() {
+    var operations = state.usage ? (state.usage.operations || []) : [];
+    var timeline = state.usage ? normalizeTimeline(state.usage.timeline || [], state.period) : [];
+    var totalCalls = operations.reduce(function (sum, operation) {
+      return sum + operation.calls_total;
+    }, 0);
+    var timelineMaxValue = timeline.reduce(function (maxValue, point) {
+      return Math.max(maxValue, point.calls_ok + point.calls_error);
+    }, 0);
+
+    state.derived = {
+      localizedOperations: operations.map(function (operation) {
+        return {
+          operation: operation,
+          localized: localizedUsageOperation(operation),
+        };
+      }),
+      normalizedTimeline: timeline,
+      timelineMaxValue: timelineMaxValue,
+      totalCalls: totalCalls,
+    };
+  }
+
   function buildEmptyState(title, message, compact) {
     var empty = element('div', 'empty-state');
     if (compact) {
@@ -263,7 +292,7 @@ document.addEventListener('DOMContentLoaded', function () {
   }
 
   function renderChart() {
-    var timeline = state.usage ? normalizeTimeline(state.usage.timeline || [], state.period) : [];
+    var timeline = state.derived.normalizedTimeline;
     chartWrap.innerHTML = '';
 
     if (!timeline.length) {
@@ -277,9 +306,7 @@ document.addEventListener('DOMContentLoaded', function () {
       return;
     }
 
-    var maxValue = Math.max.apply(null, timeline.map(function (point) {
-      return point.calls_ok + point.calls_error;
-    }));
+    var maxValue = state.derived.timelineMaxValue;
 
     timeline.forEach(function (point, index) {
       var node = chartTemplate.content.cloneNode(true);
@@ -301,7 +328,7 @@ document.addEventListener('DOMContentLoaded', function () {
   }
 
   function renderTable() {
-    var operations = state.usage ? state.usage.operations : [];
+    var operations = state.derived.localizedOperations;
     tableBody.innerHTML = '';
 
     if (!operations.length) {
@@ -321,19 +348,16 @@ document.addEventListener('DOMContentLoaded', function () {
       return;
     }
 
-    var totalCalls = operations.reduce(function (sum, operation) {
-      return sum + operation.calls_total;
-    }, 0);
-
-    operations.forEach(function (operation) {
-      var localizedOperation = localizedUsageOperation(operation);
+    operations.forEach(function (entry) {
+      var operation = entry.operation;
+      var localizedOperation = entry.localized;
       var node = rowTemplate.content.cloneNode(true);
       var errorRate = operation.calls_total === 0
         ? 0
         : ((operation.calls_error / operation.calls_total) * 100);
-      var share = totalCalls === 0
+      var share = state.derived.totalCalls === 0
         ? 0
-        : ((operation.calls_total / totalCalls) * 100);
+        : ((operation.calls_total / state.derived.totalCalls) * 100);
 
       node.querySelector('.col-name').textContent = localizedOperation.operation_display_name || operation.operation_display_name;
       node.querySelector('.col-op-slug').textContent = operation.operation_name;
@@ -404,8 +428,11 @@ document.addEventListener('DOMContentLoaded', function () {
 
     try {
       state.usage = await window.CrankApi.getUsageOverview(state.workspaceId, { period: state.period });
+      recomputeDerivedState();
     } catch (error) {
       state.loadError = error.message || tKey('usage.error.load');
+      state.usage = null;
+      recomputeDerivedState();
     } finally {
       state.loading = false;
       renderUsage();