SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31a4925f1d0dcdd398edb22340ebbc368c01327242e133efdb56f1a8fad4d02b' 
  AND token = 'DnOkrR6WjDl5EycWHzaPHntw91cwdwXeFpdK/n0yxP4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}