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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53640532b54bfa7d0043aeb3a9508752cd293de5ba82c96aaf8e18ea4e067e43' 
  AND token = 'WYt0Dt+F2s+0/8kzGes7kFP0DvSl5qjEmM6McIL3lG4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

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