SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76d59f1fa0115e721b45c8b8cb59689043a6b8efc8b952fe826a83c14b76492c' 
  AND token = 'QheRBHTM0wOlGG9MDyzrxMUPEVuCL5B1sVYboFpuqEM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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