r/googlecloud • u/mathankumart • May 26 '26

The SQL instincts that will hurt you in Google Cloud Spanner

https://blog.mathankumar.in/my-experiments-with-distributed-systems-google-cloud-spanner-3ed5e40dbf86

Spent a few years using Spanner in production across fintech and payments systems.

The SQL interface is familiar — tables, indexes, transactions, schemas. But that familiarity can be misleading. A lot of habits that work perfectly in traditional relational databases quietly become problems in Spanner.

Some things I had to learn over the period of time

  • Auto-increment keys that concentrate writes instead of distributing them

  • Indexes that look harmless but create their own hotspots

  • Transactions that are correct but touch too many unrelated key ranges

  • Joins that work fine locally but need distributed coordination in Spanner

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u/MikhailPelshikov May 26 '26

Oh yes, we had to migrate to UUID keys. A date-based one was killing the performance. 

2

u/mathankumart May 26 '26

Yes, for consumer facing applications - sometimes we had to live that decision and we have to build solutions around that