SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50a08f7879417877012f98714c454e50eef85c8229417611b2c19e43ff7fb0e0' 
  AND token = 'finZjIXlhHm21Myc8hpivyQgzdxb/mpaBNoGvTO5yZk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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