SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '429405573b6f3d405679464bd7c78cd120c2cc7afa5cb5f7cacf8839a0273b53' 
  AND token = 'JnfQVhMWYVja/1dPR8pa70p9ZifrdmT8nhkppecS/Ck=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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