SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b246d26f27736f9613b294c783f95a82b39af85fc970cd12eeebc86d769fa78a' 
  AND token = '85adVxXx+wpobQp7Kx0DBNqRpCqKqjGu9bB+6/39ySs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}