SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b5daa19f1786c64f15bf2f044bb302e67a41de173a05b690b403211dc71766f' 
  AND token = 'buQq7HADjOW1zWV3qU+JeaPpOJgOmTOQTr2wdtQcRro=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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