SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5f91152be0c1ea59afd22006db06d65df426dcfea9faf645eba29a58ad387669' 
  AND token = 'jxe+jk31aECal4dgyHlHxVj+z+NU6c/JRqkDtSDtdKI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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