SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '538562305b239692c228f8aebca0d46c525bc0acd72f08027717eb58d8d50dd6' 
  AND token = 'Yer8cGg6KhBPd9CNpp84MBL6g6wEqm8dghzIVWYSe24=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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