SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '991a10a862c19352b90d376aad5ad94e598fb46d7836a2d3b575e150998f8caf' 
  AND token = 'dihju2yPxPfnzBxUJi7eGFC+hOIGie8qiyerTJKWDV4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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