SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81b31a2ee99d3aa694c7c20b54c923952887fc5405917b2112829ae2fe3058f8' 
  AND token = 'qrZEngCRPXSrHOaH/QEymraWphOb+s+h8CEgbBDTSCQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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