SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0fc4440641d465ce9567dbe209373bdac0ee49041f3bc988a3b9da89c3a2a28d' 
  AND token = 'DKjiui5WwDiMuzXUtjM+nEzg2GNvtyDviYsw1plchvE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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