Simplify example in-memory store implementation #89

Job	Run time
Python checks (examples/cat-lounge/backend)	38s
Python checks (examples/customer-support/backend)	38s
Node build (examples/cat-lounge/frontend)	22s
Node build (examples/news-guide/frontend)	16s
Python checks (examples/news-guide/backend)	41s
Node build (examples/customer-support/frontend)	23s
	2m 58s

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