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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81a0b2c392620c19e40b4523eb0c7e7a890cb9a6931fd1f249fd91ecfcb3fb3a' 
  AND token = '+2wHLPmyXwIpwoQoGXbxbYyKRTueW8pTyFzBiH3GYEI=' 
  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