SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ed5b1ca5207392974820503763a9ca350967b625f7dfec5083f5077083af3b5' 
  AND token = 'DsVnKF6/9GRpPe4hNah0gUiDVJRa8/pk82iscIFuI9A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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