SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dcb6a0808513e47a1c9692ce5736ec7a6e946743de68fa7f6e9aea8653862065' 
  AND token = '8sAb/JMHJYlFajQQJT6af9tc9zCrxSXkhClphMafblw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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