SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6d34c9df556b193bc78a2b0f3469179159850c17f1c61e63f19befc352b3b34f' 
  AND token = 'eY1nP7v7p5vaA2NoYj4FgEkHZG324EMUDBbmcLamywE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00069

JSON explain

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