SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb7c3e4c20043e293408c5868164d8b9e9f939e08790a02ed345c7608985e8db' 
  AND token = 'nT9dsrFlJNpxn2NmVL96SNTcFsf/3jGIBFOCOCEzd1k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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