SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b3c3734812813672e0c665a402fc6a29455f0f8f5e0148f47702e2fe1bd83f3f' 
  AND token = 'wdlayacHgzLjknau1V1mYNr4S3HE3d6ivoDTmHAsKXs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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