SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3259a118b689c7f31523bc308f21dcc81765d54a4bc1bd72503a2b7293343b93' 
  AND token = 'QBBMSvkyi34nQxybBsZf+LdSgPKPwYyC3lhjwf4wAQk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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