Sending Events - Flexprice

Once you have created a metered feature, you can start transmitting events to Flexprice. Events are JSON payloads that describe usage activity and are transmitted via HTTP POST requests.

Prerequisites

A metered feature created in Flexprice
Your API key from the Admin Dashboard
The Event Name from your feature configuration

API Endpoints

Single Event

POST https://api.cloud.flexprice.io/v1/events

Bulk Events

POST https://api.cloud.flexprice.io/v1/events/bulk

Authentication

Include your API key in the request header:

x-api-key: <your_api_key>

Important: Keep your API key secure and never expose it in client-side code.

Event Payload Structure

Required Fields

Field	Type	Description	Example
`event_name`	string	Must exactly match your feature’s Event Name	`"model.usage"`
`external_customer_id`	string	Your identifier for the customer	`"cust_123"`

Conditional Fields

Field	Type	When Required	Description
`properties`	object	For Sum, Max, Latest, Unique Count	Contains the values to aggregate
`properties.<field>`	number/string	When aggregation field is set	The exact field name from your feature configuration

Optional Fields

Field	Type	Description	Example
`event_id`	string	Your unique identifier for the event	`"evt_123"`
`timestamp`	string	ISO 8601 UTC timestamp	`"2025-08-22T07:05:49.441Z"`
`source`	string	Origin of the event	`"api"`, `"worker"`

Single Event Examples

Basic Event (Count Aggregation)

If your feature uses Count aggregation, you only need the required fields:

{
  "event_name": "api.calls",
  "external_customer_id": "cust_123"
}

Event with Properties (Sum Aggregation)

If your feature uses Sum aggregation with field credits:

{
  "event_name": "model.usage",
  "external_customer_id": "cust_123",
  "properties": {
    "credits": 2
  }
}

Complete Event Example

{
  "event_name": "model.usage",
  "external_customer_id": "cust_123",
  "properties": {
    "credits": 2,
    "model": "gpt-4",
    "region": "us-east-1"
  },
  "event_id": "evt_abc123",
  "timestamp": "2025-08-22T07:05:49.441Z",
  "source": "api"
}

cURL Examples

Single Event

curl --request POST \
  --url https://api.cloud.flexprice.io/v1/events \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <your_api_key>' \
  --data '{
    "event_name": "model.usage",
    "external_customer_id": "cust-test-customer",
    "properties": {
      "credits": 2
    }
  }'

Response

{
  "event_id": "event_01K389J4M1F1NZG6XP0AMD6J52",
  "message": "Event accepted for processing"
}

Bulk Events

Transmit multiple events in a single request for better performance:

curl --request POST \
  --url https://api.cloud.flexprice.io/v1/events/bulk \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <your_api_key>' \
  --data '{
    "events": [
      {
        "event_name": "model.usage",
        "external_customer_id": "cust-test-customer",
        "properties": { "credits": 2 }
      },
      {
        "event_name": "model.usage",
        "external_customer_id": "cust-another-customer",
        "properties": { "credits": 5 }
      }
    ]
  }'

Language Examples

JavaScript (Node.js)

const fetch = require("node-fetch");

async function sendEvent() {
  const response = await fetch("https://api.cloud.flexprice.io/v1/events", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "x-api-key": process.env.FLEXPRICE_API_KEY,
    },
    body: JSON.stringify({
      event_name: "model.usage",
      external_customer_id: "cust-test-customer",
      properties: { credits: 2 },
      source: "api",
    }),
  });

  const result = await response.json();
  console.log("Event transmitted:", result);
}

Python

import os
import requests
import json

def send_event():
    url = "https://api.cloud.flexprice.io/v1/events"
    headers = {
        "Content-Type": "application/json",
        "x-api-key": os.environ["FLEXPRICE_API_KEY"]
    }

    data = {
        "event_name": "model.usage",
        "external_customer_id": "cust-test-customer",
        "properties": {"credits": 2},
        "source": "api"
    }

    response = requests.post(url, headers=headers, json=data)
    result = response.json()
    print("Event transmitted:", result)

Go

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "net/http"
    "os"
)

type Event struct {
    EventName           string                 `json:"event_name"`
    ExternalCustomerID  string                 `json:"external_customer_id"`
    Properties          map[string]interface{} `json:"properties,omitempty"`
    Source              string                 `json:"source,omitempty"`
}

func sendEvent() error {
    event := Event{
        EventName:          "model.usage",
        ExternalCustomerID: "cust-test-customer",
        Properties: map[string]interface{}{
            "credits": 2,
        },
        Source: "api",
    }

    jsonData, err := json.Marshal(event)
    if err != nil {
        return err
    }

    req, err := http.NewRequest("POST", "https://api.cloud.flexprice.io/v1/events", bytes.NewBuffer(jsonData))
    if err != nil {
        return err
    }

    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("x-api-key", os.Getenv("FLEXPRICE_API_KEY"))

    client := &http.Client{}
    resp, err := client.Do(req)
    if err != nil {
        return err
    }
    defer resp.Body.Close()

    fmt.Printf("Event transmitted with status: %d\n", resp.StatusCode)
    return nil
}

PHP

<?php

function sendEvent() {
    $url = 'https://api.cloud.flexprice.io/v1/events';
    $apiKey = $_ENV['FLEXPRICE_API_KEY'];

    $data = [
        'event_name' => 'model.usage',
        'external_customer_id' => 'cust-test-customer',
        'properties' => [
            'credits' => 2
        ],
        'source' => 'api'
    ];

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));
    curl_setopt($ch, CURLOPT_HTTPHEADER, [
        'Content-Type: application/json',
        'x-api-key: ' . $apiKey
    ]);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    $response = curl_exec($ch);
    $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);

    echo "Event transmitted with status: $httpCode\n";
    echo "Response: $response\n";
}

Data Types and Best Practices

Property Values

Numbers: Use for Sum, Max aggregations
```
"properties": { "credits": 2 }
```
Strings: Use for Unique Count, Latest aggregations
```
"properties": { "user_id": "user_123" }
```

Timestamps

Use ISO 8601 format in UTC
Example: "2025-08-22T07:05:49.441Z"
If omitted, server time is used

Event IDs

Optional but recommended for traceability
Should be unique within your system
Helps with debugging and idempotency

Common Patterns

API Usage Tracking

{
  "event_name": "api.calls",
  "external_customer_id": "cust_123",
  "properties": {
    "endpoint": "/v1/chat",
    "method": "POST",
    "response_time": 150
  },
  "source": "api"
}

Storage Usage

{
  "event_name": "storage.usage",
  "external_customer_id": "cust_123",
  "properties": {
    "gb": 1.5,
    "bucket": "user-uploads"
  },
  "source": "storage-service"
}

User Activity

{
  "event_name": "user.login",
  "external_customer_id": "cust_123",
  "properties": {
    "user_id": "user_456",
    "platform": "web"
  },
  "source": "auth-service"
}

Error Handling

HTTP Status Codes

202 Accepted: Event accepted for processing
400 Bad Request: Invalid payload or missing required fields
401 Unauthorized: Invalid or missing API key
429 Too Many Requests: Rate limit exceeded

Common Errors

Missing required field

{
  "error": "Missing required field: event_name"
}

Invalid event_name

{
  "error": "Event name 'unknown.event' not found"
}

Invalid customer

{
  "error": "Customer with external_customer_id 'invalid_id' not found"
}

Rate Limits

Single events: 1000 requests per minute
Bulk events: 100 requests per minute (up to 1000 events per request)
Response: 429 status code when exceeded

Best Practices

1. Validate Your Configuration

Before transmitting production events:

Verify Event Name matches your feature exactly
Confirm Aggregation Field exists in your events
Test with a small number of events first

2. Handle Failures Gracefully

async function sendEventWithRetry(eventData, maxRetries = 3) {
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      const response = await fetch("https://api.cloud.flexprice.io/v1/events", {
        method: "POST",
        headers: {
          "Content-Type": "application/json",
          "x-api-key": process.env.FLEXPRICE_API_KEY,
        },
        body: JSON.stringify(eventData),
      });

      if (response.status === 202) {
        return await response.json();
      }

      if (response.status === 429) {
        // Rate limited — wait and retry
        await new Promise((resolve) => setTimeout(resolve, 1000 * attempt));
        continue;
      }

      throw new Error(`HTTP ${response.status}: ${await response.text()}`);
    } catch (error) {
      if (attempt === maxRetries) {
        throw error;
      }
      // Wait before retry
      await new Promise((resolve) => setTimeout(resolve, 1000 * attempt));
    }
  }
}

3. Use Bulk Events for High Volume

When transmitting many events, use the bulk endpoint:

const events = [
  { event_name: "api.calls", external_customer_id: "cust_1" },
  { event_name: "api.calls", external_customer_id: "cust_2" },
  // ... more events
];

const response = await fetch("https://api.cloud.flexprice.io/v1/events/bulk", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "x-api-key": process.env.FLEXPRICE_API_KEY,
  },
  body: JSON.stringify({ events }),
});

4. Include Relevant Metadata

Add useful properties to your events for debugging:

{
  "event_name": "model.usage",
  "external_customer_id": "cust_123",
  "properties": {
    "credits": 2,
    "request_id": "req_abc123",
    "version": "1.0"
  },
  "source": "api"
}

API Reference — Complete API documentation
Validating Events — Check that events are being processed correctly
Troubleshooting — Fix common issues

Next Steps

After sending events, you should:

Validate Events - Verify that events are being processed correctly
Connect to Billing - Set up pricing and subscriptions

Troubleshooting

”Event not found” error

Check that Event Name matches your feature exactly
Verify the feature exists and is active

”Customer not found” error

Ensure the customer exists in Flexprice
Check that external_customer_id matches exactly

”Missing required field” error

Verify all required fields are present
Check field names match exactly (case-sensitive)

Events not appearing in dashboard

Check the Event Debugger for processing status
Verify Event Name and Aggregation Field configuration
Ensure customer has an active subscription with the feature

Documentation Index

​Prerequisites

​API Endpoints

​Single Event

​Bulk Events

​Authentication

​Event Payload Structure

​Required Fields

​Conditional Fields

​Optional Fields

​Single Event Examples

​Basic Event (Count Aggregation)

​Event with Properties (Sum Aggregation)

​Complete Event Example

​cURL Examples

​Single Event

​Response

​Bulk Events

​Language Examples

​JavaScript (Node.js)

​Python

​Go

​PHP

​Data Types and Best Practices

​Property Values

​Timestamps

​Event IDs

​Common Patterns

​API Usage Tracking

​Storage Usage

​User Activity

​Error Handling

​HTTP Status Codes

​Common Errors

​Rate Limits

​Best Practices

​1. Validate Your Configuration

​2. Handle Failures Gracefully

​3. Use Bulk Events for High Volume

​4. Include Relevant Metadata

​Related Documentation

​Next Steps

​Troubleshooting

​”Event not found” error

​”Customer not found” error

​”Missing required field” error

​Events not appearing in dashboard

Prerequisites

API Endpoints

Single Event

Bulk Events

Authentication

Event Payload Structure

Required Fields

Conditional Fields

Optional Fields

Single Event Examples

Basic Event (Count Aggregation)

Event with Properties (Sum Aggregation)

Complete Event Example

cURL Examples

Single Event

Response

Bulk Events

Language Examples

JavaScript (Node.js)

Python

Go

PHP

Data Types and Best Practices

Property Values

Timestamps

Event IDs

Common Patterns

API Usage Tracking

Storage Usage

User Activity

Error Handling

HTTP Status Codes

Common Errors

Rate Limits

Best Practices

1. Validate Your Configuration

2. Handle Failures Gracefully

3. Use Bulk Events for High Volume

4. Include Relevant Metadata

Related Documentation

Next Steps

Troubleshooting

”Event not found” error

”Customer not found” error

”Missing required field” error

Events not appearing in dashboard