SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7626b0bf1a91ccb65286620314be1e53f818b2b1ec77b983a47f0f12437eeb84' 
  AND token = '2j3cIvfYi0ug+jmh8BY/bVuyBH8DpMmLhMiVJhZXlAk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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