SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e5b44ed2901239c40fe5881e3d97626ff3724d4991967b532a641920d20376b' 
  AND token = 'KQph+z9/VsrDlG1XLiDYQ0IZhS7KXHN00+bUkkwxx5s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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