SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f9a276ac975b4ee80ae84fcd7e7c14eecb3a0601c37bf1fd77fc32060fd458f9' 
  AND token = 'vxMhkZaJnHzMzDWz4NO7qrq6MHHfrvyTuc4N1yRaKw0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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