SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a50f0eac049c147d4836bb2840d495a809a39f82d1f023987af3030b5d487f6f' 
  AND token = 'I/xG8QAEIECm6U12VvbU1l9Zwic/xyNsqYwxeKrUCb0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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