SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '868dabb0535a2be35d489136fc9dfbdc9a43a330944d54a3ff5b95a8153777a0' 
  AND token = '3r1vvi5jlizaytYMDuuDJC49mzOL4SmowWQtCuD1JT0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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