基于Android Studio与Firebase的单机问答游戏Firestore读取定价咨询

Hey there! Let’s walk through your Firestore read count and pricing questions—this is a super common concern when building quiz apps, so I’ll break it down clearly based on your setup.

First: How Reads Are Calculated for Your Database Structure #

You mentioned your structure is:

Project → Category (collection) → Auto-generated ID (document) → Custom object (includes Question array, correct answer, options A/B, etc.)

Let’s clarify two key scenarios based on what’s in each document:

• Scenario 1: Each document holds exactly 5 questions (ideal for one round)
  If you’ve structured each document to contain all 5 questions a player needs for a single round, then every time a player starts a round, you’ll only make 1 read request to fetch that one document. Firestore counts reads per document, not per piece of data inside it (as long as the document stays under 1MB, which it will for quiz questions).

• Scenario 2: Each document is a single question
  If each document only holds one question, a 5-question round would require 5 read requests (one for each question document). This is less efficient, so I’d recommend grouping questions into docs of 5 if possible to minimize reads.

Pricing Breakdown #

Firestore’s pricing is straightforward, and the free tier is more than enough for most early-stage apps:

• Free Tier: 50,000 read operations per day. Let’s crunch the numbers:
  • Scenario 1 (1 read per round): That’s 50,000 rounds of play daily—way more than enough for initial user bases.
  • Scenario 2 (5 reads per round): That’s 10,000 rounds daily, still plenty for a new app.
• Paid Tier: Once you exceed the free tier, it’s $0.06 per 100,000 read operations. Even if you hit 1 million reads in a day, that’s only $0.54—super affordable for scaling.

Pro Tips to Minimize Reads (and Costs) #

• Cache questions locally: Once a player fetches a set of questions, store them on the device using SharedPreferences or Room. If they play another round in the same category, reuse the cached questions instead of making another Firestore call (just refresh the cache periodically if you update your question bank).
• Randomize efficiently: If you want to serve random questions each round, don’t fetch all documents in a category (that would count a read for every doc!). Instead, add a random number field to each question document (e.g., random: 0.234), then query for documents where random falls between two values to get a random subset. This way, you only read the exact number of docs you need.
• Batch read if needed: If you do need to fetch multiple single-question docs, use Firestore’s getAll() method to fetch up to 10 documents in a single request—this still counts as one read per document, but it’s more efficient than making separate network calls.

内容的提问来源于stack exchange，提问作者J. Lo