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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df12888b6eb1ac4c955d55203bbfd62ee42e5c315c606acad34a61d614b3f421' 
  AND token = 'OUqd/F81SWTgPdECwKgrs582cRqJB3uFFClYKlVggUc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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