SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79f736dfb04b954fec3865365e722c8f2d3c8e1656baacee204a5a6fd9cf1b51' 
  AND token = 'upAlmQ0cjPYwqKhIW4c0RPeg/TMkAAtXq4R6HU58itM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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