SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e4c38e8e73504ca2d6cc5f937506236250f53804c6ca2a537cd76c08a29670f4' 
  AND token = 'RgQHPz6bB1WJ0aJVSjklhMIZT+cyBGC6HQLhCZLr7xQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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