SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '34bc6263ce1a8314677843f8cc046b13982d2b6d27e5cdfc03ce98beeacf91ac' 
  AND token = 'QkAvoQoWCh4N26eEt8OC+EDemAL6iQeD0CdZ9vzMM7E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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