SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f90ce1e917e57a03a060c6bded3548310438fd28d0757af01c5ac1c756763ea4' 
  AND token = 'UdVAB58SpDSLiBxGPE0FXwah8tQKCNTfoSCJwAAqJ80=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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