SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42ebc35831ce4808ad408b6c19362fc1cdfa1e1c72d10305c92f6362f395e7de' 
  AND token = 'UklhLt1aRdzcmV/JDcWa5G+pRd+t7VYXd0whOqPk768=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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