Here are some useful links for further reading (we have discussed most of these systems in Grokking the Advanced System Design Interview):

1. Dynamo - Highly Available Key-value Store

2. Kafka - A Distributed Messaging System for Log Processing

4. Paxos - Protocol for distributed consensus

5. Bigtable - A Distributed Storage System for Structured Data

6. Gossip protocol - For failure detection and more.

7. Chubby - Lock service for loosely-coupled distributed systems

8. ZooKeeper - Wait-free coordination for Internet-scale systems

9. MapReduce - Simplified Data Processing on Large Clusters

10. Hadoop - A Distributed File System