SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff7f409ee358fac229a58a63a68138624beba2262d9d0f788b71e3fb426d335c' 
  AND token = 'Kh+sJ3WqE4OhTBCL37Lsw+A40c1BG/TyPAwghKvuVHo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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