SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8fc0a3444d347a0728ef58c2892e7fed7043c64ee41ac1a750ffaa6d0f589636' 
  AND token = 'q8JrEoxL1tvo7L41HkVt1HkPkU01wrxaVHXZt/eTHIA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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