SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '79370d3f3e3418c1adb78c778550e5c75df827999c65c5c5c06a25b5266a59b4' 
  AND token = 'XllIKTPvA+KEXt1BL+nGz5z4KK6NeVExT1EHUTgmjjM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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