SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8d7adb7892dfdcb5cc5d3ff5f7774e3618f15ee021bb7154dc2535fc1408f3b' 
  AND token = 'fSDV3jJhGsN/Ms8ja2z+jQDpOwc8aBz+alfqk9LrNX4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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