SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '357c713bb96315e53e1f84cd90e3bb4087091adf895ef65ccc7f5dabe9586146' 
  AND token = '2SkRT2DvFsf+clvDv7NHHfo9nJX3mYPgRL2kYhXLwKE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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