SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9903ed2a81b8331bf445ab36efcdcf25f1239a5da611fc7d044f3beb6e250f00' 
  AND token = 'EWIQfPmIYup1j6SdrrCTvrMcG3Fl8FqQsjg2Ss0hWl4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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