SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '268801d6afa4b3bcce1bcb364251d85d9781c86cc8c99cd051d885922b47f30f' 
  AND token = '353ywldtv9OxXnFKxBoxbTwqQd5eVNh0PPfxXEuUw2c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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