SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '273a37669901abc2744d486bf1c870cb919adc453e44b85a3a4f79e0b7864f51' 
  AND token = 'NmYVlwBG3SdA5BW52wuxvxkkQFVk5eWmsojORRogqLs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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