SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39e7f1bcfe315dc9ef6397bc135f333953b798363593209c2000dde41bed031d' 
  AND token = '/iiTkDNYujVxG8quSIiHfFtqJ098DcSDn7+eoKbJEO4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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