How to Monitor Event Frequency in Amplitude

import * as amplitude from '@amplitude/analytics-browser';

// Initialize at app startup
amplitude.init('YOUR_API_KEY');

// Log events as users interact
amplitude.logEvent('Payment_Processed', {
  currency: 'USD',
  amount: 4999,
  plan_tier: 'professional'
});

amplitude.logEvent('Dashboard_Loaded', {
  load_time_ms: 1240,
  user_segment: 'power_user'
});

// Example: fetch daily event counts via REST API for custom alerting
async function checkEventFrequency(eventName) {
  const now = Date.now();
  const oneDayAgo = now - (24 * 60 * 60 * 1000);
  
  const response = await fetch('https://api.amplitude.com/2/events', {
    method: 'GET',
    headers: {
      'Authorization': `Bearer YOUR_API_KEY`
    },
    body: JSON.stringify({
      event: eventName,
      start_time: oneDayAgo,
      end_time: now
    })
  });
  
  const data = await response.json();
  return data.series[0]?.data || [];
}

const counts = await checkEventFrequency('Payment_Processed');
const lastValue = counts[counts.length - 1];
if (lastValue < 10) {
  // Send alert to your system
  console.error('Payment frequency below threshold:', lastValue);
}

import fetch from 'node-fetch';

const monitorEventFrequency = async (eventName, threshold = 0.2) => {
  const now = new Date();
  const yesterday = new Date(now.getTime() - 24 * 60 * 60 * 1000);
  const twoDaysAgo = new Date(yesterday.getTime() - 24 * 60 * 60 * 1000);
  
  const getCount = async (start, end) => {
    const response = await fetch('https://api.amplitude.com/2/events', {
      method: 'POST',
      headers: {
        'Authorization': `Bearer YOUR_API_KEY`,
        'Content-Type': 'application/json'
      },
      body: JSON.stringify({
        event: eventName,
        start_time: start.getTime(),
        end_time: end.getTime()
      })
    });
    const data = await response.json();
    return data.data?.total || 0;
  };
  
  const yesterdayCount = await getCount(yesterday, now);
  const twoDaysAgoCount = await getCount(twoDaysAgo, yesterday);
  
  const changeRatio = (yesterdayCount - twoDaysAgoCount) / twoDaysAgoCount;
  if (Math.abs(changeRatio) > threshold) {
    const direction = changeRatio > 0 ? 'increased' : 'decreased';
    const percent = (Math.abs(changeRatio) * 100).toFixed(1);
    console.warn(
      `Alert: ${eventName} ${direction} by ${percent}% ` +
      `(${yesterdayCount} today vs ${twoDaysAgoCount} yesterday)`
    );
  }
};

await monitorEventFrequency('Payment_Processed', 0.2);
await monitorEventFrequency('Feature_Click', 0.15);