SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6fc754fcd939c539bed576a3aa2cb4307c50723709d61760aba7c3650c67313' 
  AND token = 'z9ybAYfWaI4YnSClFohsAHLm4mDbkuP4BdPfF4yjeqg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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