SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50ae6b0a673c37c48a0df01168782353bda10c56a2916906c76d487bb3d94efd' 
  AND token = 'TpDMGTnYthsiUAe4ffiPYfef82F3uWxbheyZdDHKn4s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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