Read path

After a read request is directed to a specific node, it first checks if data is in the memory cache. If so, the data is returned to the client

If the data is not in memory, it will be retrieved from the disk instead. We need an efficient way to find out which SSTable contains the key. Bloom filter is commonly used to solve this problem.

The read path is shown in the picture below when data is not in memory.

1. The system first checks if the data is in memory. If not, go to step 2.

2. If data is not in memory, the system checks the bloom filter.

3. The bloom filter is used to figure out which SSTables might contain the key.

4. SSTables return the result of the data set.

5. The result of the data set is returned to the client.