SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'bd2b5308d69982ac0362d49b0e3dda0988cf1d6685f843b182f5cae824493b79' 
  AND token = 'fSgh2+10WCM/ZnUHCfzSe6WcjE+XLLIyUVzLBkfyKPw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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