Sharded Counters

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In the design of the sharded counter system for Twitter’s tweet metrics, where separate counters are created for each tweet (e.g., like counters, reply counters, retweet counters, view counters), could you provide more insight into the system’s approach to allocating physical resources?

  1. Are individual physical machines dedicated to hosting counters for specific tweets, or is there a shared hosting mechanism where multiple tweets might reside on the same machine?

  2. Can you elaborate on the dynamic adjustment mechanisms implemented for the allocation of counters to machines? How does the system adapt to factors such as varying load, tweet popularity, or other performance considerations? Are there automated processes that optimize the allocation based on real-time conditions?

Course: Grokking Modern System Design Interview for Engineers & Managers - Learn Interactively
Lesson: Detailed Design of Sharded Counters

2

Hi Rahul,

  1. The physical resource allocation involves a shared hosting mechanism, where multiple tweets coexist on the same machine. The system dynamically adjusts shard numbers based on real-time requirements. Monitoring mechanisms track write loads on all shards, effectively utilizing feedback to route requests.
  2. Load balancers are used to distribute requests and manage shard allocation dynamically. Automated processes continuously monitor and optimize allocation to ensure efficient resource utilization and performance.

Additionally, we have covered such details in Detailed Design of Sharded Counters.

Thank you.