SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '876004a7ff8df594465305adf6ade9150113245081053b9af17b602965462d03' 
  AND token = 'wLck1L8jmv+WbZzV7chGXd8E6wdcwZ12zmRm56Tu/2o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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