SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3a94f498d0e3c1afe1d6e82624948b744aedbfdd43f479728722d6e48041bc7' 
  AND token = 'EDqK1aOMtLQOR0aQBABv6ZxARjcFxaQOgDvVrkqgO/o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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