SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '83c43bff2bb793b481f0a5a14fac7cadba96f6b9a851df7439e363acf8de5fde' 
  AND token = 'tU2dxow5TKqJ8O825xL//m+cZLZU2CAa8aqCo2zslGg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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