SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '148229c1b0243f800ea22932e68a96020e2bede7661e4f59fcea85ac4452b3c2' 
  AND token = '91SJjXXGwDEvshtEnLQdtrR+/PRGXwXy9By2JNLkMUE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00062

JSON explain

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