SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7fb5bf74282ca2b1576e9a589a684167177390092c014fcc3e806fc7dcaeb96f' 
  AND token = 'JyZEnouCYZJ7b947Qv2teinsbnjsIWdftaxYm23JaqQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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