SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c15851314e9913b5a5aae83d372c0be6e585410878065411da0fb3f83f4d716' 
  AND token = 'wCUPnCOeb7fKWTxTcn9xRFOD8638bjKOjQNRgMDJCsU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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