SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1b0849257633b9d8ee1eda09f684eca701f5547a3c6c43cbfeda613a474b9016' 
  AND token = 'D8buZDFllm/+qjq0tyLqETmzCZzjRl5VcvZqJWTBBso=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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