FCM免费版使用限制技术咨询：百万级周活用户场景

Hey there! Since you're working with a large user base (1-2M weekly active users), getting these FCM free tier limits right is crucial. Let's break down each of your questions clearly:

1. Are there daily/weekly/monthly limits on Firebase calls in FCM free tier? #

FCM's free tier doesn't enforce hard fixed limits on daily/weekly/monthly call counts. Instead, it uses a dynamic "fair use" quota system tied to factors like send success rates, message volume patterns, and adherence to Firebase's policies. For most legitimate use cases with your user scale—sending targeted, non-spammy messages to active users—the free tier should handle your volume. That said, if you send an unusually large burst of messages in a short window, you might hit temporary rate limits, which will return 429 errors that you can handle with retry logic.

2. Is there a limit on concurrent calls to my FCM server account? #

Yes, the free tier does have concurrent request limits. Specifically, FCM's HTTP v1 API (the recommended modern endpoint) enforces a rate limit of 1,000 requests per second for free tier projects. If you exceed this, you'll get 429 "Too Many Requests" responses. To work around this, consider using batch requests (you can send up to 500 device targets per batch request) to reduce the number of individual API calls, and implement exponential backoff for retries when you hit rate limits.

3. Can the data payload exceed 4KB in FCM free tier? #

No—this limit applies to both free and paid tiers. For Android devices, the data payload alone can't exceed 4KB. For iOS devices, the total payload (combining notification and data fields) is capped at 4KB. Any payload over these limits will be rejected by FCM, so you'll need to keep your data payloads concise or use alternative methods (like hosting larger data on a server and sending a link in the payload) if you need to share more information.

4. Is there a limit on the number of device groups I can create? #

Absolutely. For FCM's free tier, each project is limited to 1,000 device groups total, and each individual device group can include a maximum of 20 devices. If you need more device groups or larger groups, you'll need to upgrade to Firebase's Blaze (pay-as-you-go) plan, which removes these restrictions.

内容的提问来源于stack exchange，提问作者Ameeta Jayaraj