SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cfb6a8e768a2878e5f4109b31f30ec713c951dad06f0a28671214035d0397640' 
  AND token = 'eSSVgFLmw8/kNRxLpdKoM5HeTuj3zC/ASfcsQKoKvL8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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