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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8d50294d6ac2406ffdcd7b23a08422f2144665f9f5b84992972dd6ef0571c12' 
  AND token = '/0hJ2YYcOAAJ4YTlkQSWq2LDin7m0Vek1pUYNiD7Mh8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE								Impossible WHERE noticed after reading const tables