SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'fbfd9e3b847d7bbff0301487b306cdebba3242944e809d4a4549553e915f7ac7' 
  AND token = 'XQTGszy3lrtRztNPft9AGhJA75p9ytW7/tGFAz7wT54=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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