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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79521bbce0e46817d7cc24479978e7d7830f28e0e8d61ebf35d40251768bee68' 
  AND token = 'c4MHSR1GZHzzzyqZVRCUmv9AsUkOXGp6iFXm87Ck/VQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

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