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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '873ab21ff134b7eac8af655111856cb66f24f140361d9302de4abe3608375557' 
  AND token = '9jqWe+7E5BTOczIzBdebfEoqr3QmQU71WX1mEjv775E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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