SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a50c6bc87b1c31025193e2200d4187290bbb656696408a7104ea67780a4b8457' 
  AND token = 'pcGCFxV499UVtOP//KSIGYfdK+PBFywtuWMHQFZJCSA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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