SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51892ffea3ece56c3b722fd58a3d9fe9de0bd2188b5f9c8b4c64f8bd6c07de64' 
  AND token = 'abHqZxpYK8JCNGHAFzylo2+mi1ZvWa2osgJiLeLQ3Yc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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