Challenge 1: Build a Simple Queue — Possible Solution
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Producer:
127.0.0.1:6379> RPUSH image-jobs "resize-image:1"
(integer) 1
127.0.0.1:6379> RPUSH image-jobs "resize-image:2"
(integer) 2

Worker:
127.0.0.1:6379> BLPOP image-jobs 0
1) "image-jobs"
2) "resize-image:1"

WHY THIS WORKS AS AN ANSWER
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Both RPUSH calls append to the TAIL of the list in the order called,
giving image-jobs the contents ["resize-image:1", "resize-image:2"] —
the first job pushed ends up at the front (head) of the list, per
Chapter 3's ordering rules.

BLPOP image-jobs 0 blocks (waits) until an element is available at the
HEAD of the list, then pops and returns it — since resize-image:1 is
at the head (pushed first), it's the one delivered to this worker
first, following standard first-in-first-out queue order. The 0
argument means "wait indefinitely" rather than timing out after a
fixed number of seconds.

A second call to BLPOP image-jobs 0 from another worker (or the same
one again) would then receive resize-image:2, since the first job was
already removed from the list by the previous BLPOP.