SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d8e9c409b902204e57e55d8681fb0a4c168f7d0125403bfbda43fbb99219151' 
  AND token = 'qJ+0afFxfv85arbgN1sRKBMUm+1lnXTmJMzS06TsoaU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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