SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5d547562e51c6a1692084ccd73050a52282e1c7578a1e630da02b1f1b6101b2b' 
  AND token = 'XLVrWsGgBKp/DVWwVOaK7+LamSeQelDLFnyPShsieko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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