I find the query cache is removed in MySQL 8.0. The official MySQL team published a blog post explaining why they removed this feature:

The query cache has been disabled-by-default since MySQL 5.6 (2013) as it is known to not scale with high-throughput workloads on multi-core machines. Rene confirmed this in his post yesterday, but it has also previously been mentioned by Stewart Smith, Domas Mituzas (update: and Kristian Koehntopp).

Assuming that scalability could be improved, the limiting factor of the query cache is that since only queries that hit the cache will see improvement; it is unlikely to improve predictability of performance.  For user facing systems, reducing the variability of performance is often more important than improving peak throughput

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We also agree with Rene’s conclusion, that caching provides the greatest benefit when it is moved closer to the client:

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With the current limitations noted, the query cache will continue to be supported for the life time of MySQL 5.7.  MySQL 8.0 will not support query cache, and users upgrading will be encouraged to use either Server-side Query Rewrite or ProxySQL as a man-in-the-middle cache.

It appears that the decision to remove this feature is largely tied to its implementation approach. Additionally, for transactional databases, predictable performance is more critical. Given the relatively low complexity of queries, utilizing a query cache may not yield significant performance gains.

But I use PolarDB MySQL and have some complex query execute ON in-memory-column index(IMCI). At times, I can indeed benefit from the query cache feature. And PolarDB MySQL has the "fast query cache" feature, they claim to have resolved the query cache issue mentioned above, Should I use fast query cache or use middleware(ProxySQL) to cache query result as suggestion of official MySQL team?