SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f3715b9988126e2b188dbff1400b17f161ddbeabf54e6cea515d3aed2df96c52' 
  AND token = 'uJGUHLYhPsIOZiR35os/AdXeyLzEPQ7XSR+QFgjc0Ww=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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