SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21bb7b6717887c58a05c0f81f6988c4779637762618524b7c21b84e818741cfa' 
  AND token = 'JEV/kle0+2RT2zRy7XJgQYbuBxLCsZoVTbq5hof4rgU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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