SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '4d19cba6e0cc03018f9ccb23ae437ff7e57939936043c585bf0c0f3fd1e0a849' 
  AND token = 'v3WiQm0VyhZGRHluZ78fX+e4b8wSfufJd5Bd/KN5fZA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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