SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56534ae758302d0268a23df491d1a00833f09e88adbe080c83fc0afdde00b663' 
  AND token = '9q6Z+9KaZ5ecQg0d1fDJqerxKFmjGxQOvHUiLc61MZI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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