SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f68f98a541792ae2fd9a7c77b854b40e94500472d49e35501d10a26ed8d77ce' 
  AND token = '3kh5vVET+D4szFC7DN/NHLRmJcBZzDZBnQVRv2AAjx8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00057

JSON explain

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