SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef5ec857ff574616fc4792ed69d171ba3481931fcd432e8abfa70e6f097d5490' 
  AND token = '8v+pK8jkFgcbbjMmF5Eu3FHmu8vayK1ZTv8QOSud5Kw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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