SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1dcf194a52068cc9ff4ba5df01a7df2e404bd9b534a9b36943fc18f956ac412d' 
  AND token = 'mQIBdznhUrqYJ/sz1YPA43AzIHabACdAxizvghjkw/g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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