A hotel room booking example

Before we jump into the different attributes of a distributed system, let’s set some context in terms of how reads and writes happen.

Let’s consider an example of a hotel room booking application (Figure 2.1). A high-level design diagram helps us understand how writes and reads happen:

Figure 2.1 – Hotel room booking request flow

As shown in Figure 2.1, a user (u1) is booking a room (r1) in a hotel and another user is trying to see the availability of the same room (r1) in that hotel. Let’s say we have three replicas of the reservations database (db1, db2, and db3). There can be two ways the writes get replicated to the other replicas: The app server itself writes to all replicas or the database has replication support and the writes get replicated without explicit writes by the app server.

Let’s look at the write and the read flows:

Write flow:

User (u1) books a room (r1). The...