SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1b8b61991c0677622fadccadca6f3d8bf38e7cf861a508aafde522caa7e984bb' 
  AND token = '76dydETJKPl4IoqSxg5ShEinnDZhSagwEYHrcQUiDy8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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