SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83c20e2208992433d2e3b8b7ecd69401abc87d1f942275fcd78bc0777aa4cdca' 
  AND token = '7k30L6/BVcGUQipUXgS4LKYTFnDzj5BZYf6GvS+nIaY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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