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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a07d1ffb46829a21fade351e70684352ce94dcfcd22f0f39bc3cfce708f188d1' 
  AND token = '15a5071z3jFgwLXbAiFFpHoy4qOwcECDEQfQwHMHCCk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

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