SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31e31d6b510081aea7a453dac899cf842d098e945d38927465c4da2403bc09c5' 
  AND token = 'Vj1fwiaXbPBg7OJMqZ/S2COyvG3IKDvLmfL7UxTGc1c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}