SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7f3a87d6337a410acd28563273180987f1e02cd36fc7c6d82eb6126cc9779c08' 
  AND token = '8bPz8BqSMBHjtaarNsH98HduJOYTA4SDksVObP6dpSc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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