SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '9dc5506ad3917591ac836e062f133f2ad708ca7f1ae102c7db40b97381665bad' 
  AND token = 'blVdjNLgp+i4/XzhafRkbFhAETbxqsRsTo/IzRE2JDA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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