SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '392280e0041d1dfe0d2b475b0b6e7462c755d28ea47486721bc715067b73b111' 
  AND token = '6SGvaeujypxfvMkK50LmcFaStGy2TPjWtIGTc+13aJ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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