SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '789142c712ae0d02d2b89f37fde276c70d6f349c5f9d5fec0580a541c78fe9d5' 
  AND token = 'fKugv3EMhXIZ0zRmRecJO9GpSFrSmznaXMujzq+pun8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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