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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b241fef624388bf87f69a0767b6dd3f36e89408e7be7b0d04e328e49d1ba44e' 
  AND token = 'PiVJDr8WJVRyhuycIOL+Rq8GRWdwePuKgnA/qHFdASc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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