SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af91db32bf323788a7084d77ef40f8ff728cb6326a62bd99c653bb6e8aa2105b' 
  AND token = '59KO9TTYkRBDWJO7jtyn3VZc+LcJGpvxyhadHd/lhqY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}