SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '251df22fc566ff60935bacbfb441f99976eea1ed13201eb83288c537a48641c1' 
  AND token = 'hXShOef3OZVCSzfDYF8Ggg3MfddxP+nDeUYb3K2TfKY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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