SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29def1cf291d4803f26c3f303e340dfc8e4ee040d80e939843871763328e20cf' 
  AND token = '/QbYvqz8MV7VRCYPAqMF4e68kLk3HVT755oICKagzoQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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