SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8fb844d014ee5901b70c9f70d877a20768c37c7815f185acb61074ce2ae3e6f2' 
  AND token = 'mHubkA9ZrlnBMEFZ6vPHYdkRtu8pz+2WZLdAXvDOe2c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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