antirez, founder of redis, has covered some advanced topics in his blog <a href="http://antirez.com/latest/0" rel="nofollow">http://antirez.com/latest/0</a>
Redis University is free. The quality of materials is superb.
I fully prepared for Redis Certification exam using only Redis University materials / Official redis docs.
<a href="https://redis.io/university/" rel="nofollow">https://redis.io/university/</a>
In case you are interested in internals, I found code crafter to be very useful for learning.<p><a href="https://app.codecrafters.io/courses/redis/overview">https://app.codecrafters.io/courses/redis/overview</a>