SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68b8ec49045ac6d4a2d4830cedb042653a55a69e29971d6b4290c18961b34f06' 
  AND token = '/8JxckapOJCHDlrUyYcKPOMU9uMNICmoDYRmzXE65Qw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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