关于Google Play Developer Api的Purchases.products接口验证响应缓慢的问询

Hey there, let's break down your problem step by step based on the details you've shared:

Possible Causes for the 20-40s Delay #

1. App-Specific Soft Rate Limiting (Throttling) #

Your suspicion about throttling is very plausible. Google often applies soft throttling to requests when a single app (even under a valid service account) sends more traffic than their backend expects for that specific app. Unlike hard quota limits (which return 429 errors), soft throttling slows down responses instead of blocking them.

The fact that invalid receipts return in ~1 second makes perfect sense here—Google can reject invalid data immediately without querying large datasets, so throttling rules don't apply to those requests. And since other apps under the same account work fine, this throttling is likely tied specifically to this high-traffic app.

2. Large Purchase Dataset for the Target App #

Given your app's popularity, it might have an enormous volume of historical purchase records. Validating a genuine receipt requires Google's backend to look up and verify against this dataset, which could take longer than usual if the dataset is particularly large. Invalid receipts skip this heavy lookup step, hence the faster response.

3. Suboptimal HTTP Client Configuration #

Even though you're reusing the AndroidPublisherService instance, the underlying HttpClient might have default settings that aren't optimized for high concurrency. For example, the default MaxConnectionsPerServer limit could be too low, leading to request queuing during peak traffic periods.

How to Confirm if You're Being Throttled #

Here are concrete steps to verify:

• Check Google Cloud Console Quotas: Navigate to your project's Google Cloud Console → IAM & Admin → Quotas. Filter for the Android Publisher API and check if you're approaching or hitting any quota limits (like requests per minute). Even if you're under the hard limit, look for throttling indicators in the usage metrics.
• Inspect Response Headers: Capture the full response headers when calling Execute(). Look for Retry-After (explicitly tells you to wait before sending more requests) or X-RateLimit-* headers that show your current rate limit status.
• Enable Detailed API Logging: Turn on verbose logging for the AndroidPublisherService in your .NET code. This will reveal any warning headers or throttling-related messages from Google that aren't visible in the basic response.

Alternative Purchase Validation Solutions #

Given your app's 16k daily requests, these approaches will help reduce latency and avoid throttling:

1. Real-Time Developer Notifications (RTDN) #

Instead of polling Google's API for every purchase, set up Real-Time Developer Notifications. Google will send a webhook whenever a purchase is made, canceled, or renewed. You only need to validate the purchase once when you receive the notification, then cache the result for future checks. This cuts your API request volume drastically.

2. Cache Validated Purchases #

For active valid purchases (e.g., non-consumable items, ongoing subscriptions), cache the validation result in a fast datastore like Redis or Memcached. Set an expiration time based on the purchase's validity period (e.g., until a subscription renews). This eliminates repeated API calls for the same purchase.

3. Optimize HTTP Client Settings #

Tweak the underlying HttpClient to handle high concurrency better. Here's how to adjust your code:

var httpClientHandler = new HttpClientHandler
{
    MaxConnectionsPerServer = 50, // Adjust based on your peak traffic
    AllowAutoRedirect = true,
    UseCookies = true
};

var httpClient = new HttpClient(httpClientHandler);

var service = new AndroidPublisherService(new BaseClientService.Initializer
{
    HttpClientInitializer = credential,
    HttpClient = httpClient
});

This increases the number of concurrent connections allowed to Google's API, reducing queuing delays.

4. Async Batch Processing #

If you have multiple purchases to validate for the same user, run the validation calls in parallel using Task.WhenAll in .NET. This avoids sequential delays, just make sure you don't push beyond safe rate limits.

Additional Tips for Your Current Setup #

• Check App-Specific Metrics: In the Google Play Console for this app, look at the "API Usage" section to spot unusual latency or error rates for purchase validation requests.
• Test a Separate Service Account: Try using a dedicated service account for this app. If latency improves, it confirms the throttling is tied to the original service account's traffic for this app.

内容的提问来源于stack exchange，提问作者Lars Blaabjerg