SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '158a666beed904e4cd5eddaf851063d257490874a0116bd664025ffe71b168fc' 
  AND token = 'VK/uRL5YHYX/VrnRUQTwMjXsat73EfLhyw2WEBd9QqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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