SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e891a9c30ecf1242ac68931372f37865873324893255888d79f713d1b8b8e38' 
  AND token = 'pAazUuH2oEj8xWtn6PGUZe00fwElKVFoQzUwtopyzTM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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