SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a4ba94fd4d24d5fe68a9048b43d468581f0156864357cb0796d043961c1472df' 
  AND token = 'ZW7lfP3qdPi0RcxVb+z0NRgxwmvSkJEMmDLHznexmns=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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