SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '306c8b4309e5831fe47fc2acc4b43934119e3d2d62d92d88471142a5e3d7e4a5' 
  AND token = 'f1LliPCTCsFAJHkHHK7WL4SlZU0UP3puQism2USdZfI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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