SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3d8cb2eb876204b89a7596cc9aceeee82a5e3af37ff30999270f6db70373d3b' 
  AND token = '73+7BS8hBEbCp8gEVBgZitBiaMQBf61uMiAfPD1atyc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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