SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1936f1e2bcb69e3d836f7f3f41fbfc29e89f585ca131b6e455b76d66d9aaa276' 
  AND token = 'YZQjjrqoFhU+wJdvl2fR0xww9HQj6BEnnKfhhP3Y0ag=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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