SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b6858c534cb171c0393c01b8b07327b759f818864291dbe16c6aee5b29c45b8' 
  AND token = 'K/gdE40zFmrXASkLy2cZaV+1LSGEANuE+TYNHZvWroM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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