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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81cdb2a59c6a7e203b35ca005c3fd71a5a08619c121cb456a96fddbb0dca2c02' 
  AND token = '0ZFGpLb76AYV5tQtnI1mqwc6vLanILLsjYN58u5c3kk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

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