Saving Data on Android

Limita/ons
As mentioned earlier in this chapter, Realtime Database is built to handle high-
traffic apps, but it still has some limits. You'll examine some of those limits next. All 
of the limits that will be mentioned apply for the Realtime Database in general, not 
for the free plans.
Realtime Database allows you to have 100 simultaneous connections for free, but 
100,000 simultaneous connections in a paid plan. This doesn't mean that your app 
can have 100,000 maximum users because not all of your users are connected at 
once. Simultaneous connections are devices currently connected to the database.
A single database can approximately send 100,000 responses per second. Responses 
are anything that comes from the database, like read operations, for example.
When writing to the Realtime Database, the maximum size of a single write event is 
1MB. That write event includes already existing data at the location that you're 
writing to plus the new data.
When it comes to the data in the Realtime Database, the data is stored as a JSON 
tree, as you learned previously. The maximum number of child nodes must be less 
than 32 levels deep, the maximum length of the key is 768 bytes and the maximum 
size of the string is 10MB.
Saving Data on Android
Chapter 15: Usage & Performance
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Reading and writing operations are also limited. The size of the data at a single 
location in the Realtime Database should be less than 256MB for a single-read 
operation. To perform a read operation at a larger location you should consider using 
pagination with a query or some other method. The maximum time to run a query is 
15 minutes. The total number of cumulative nodes in a path that you want to listen 
to or query needs to be less than 75 million.
The Realtime Database can handle 64MB per minute through simultaneous write 
operations on the database. The maximum size of a single write request is 16MB if 
you're writing through the SDK and 256MB if you're writing from a REST API.
To avoid those limits and scale your Realtime Database data, you can have your data 
divided across multiple Realtime Database instances. Since the limits mentioned 
above only apply to a single Realtime Database instance, this is a way to avoid them. 
Having multiple database instances also allows you to balance server load and 
improve performance. This concept is known as