SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'b6dc8db80bdc6fe24f78ceceeac719d6356739122f17eb8286808f0a29679898' 
  AND token = 'mzTxDd9lmIYB1CC86knllbWRrc6QDApVwaIvKNFRimo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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