SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c301655a4d552db2913cff0a31edcaa0e72ee0a88b0975f337569607f68c052f' 
  AND token = 'mfnt351FHI/v9pGToYmOp9fEwSvX1IYhgoa/X2wjih8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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