SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6dcaaaa7544a40cfc1ca648aa8738d914aa802700fc456b360433145cccada19' 
  AND token = 'PsgMKktOl73nbcUQnAtjSc0jLHzIMahItP6gja7AQh4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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