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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef2828e52aa74610e661766d40e61388456dcc66203bd641ca37497120d0c370' 
  AND token = 'SJsFrlIsK9eTy8Ce0BBdSaPFQi0GWPPegYgi6MOnGgE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

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