SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff3969b3c45a21f8004a8c2718736da85aa55b0c3ed6b9dd20f49fb3d365fd37' 
  AND token = 'rvFR9vVpGm7G6QRMAXl2Xtgj1sxa4q+bhi4SPapdi+A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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