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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20121aeb81a9eb8e5404cb00251a6ffca5a6583183188787052b5b98462f47be' 
  AND token = 'mXSx4CFu8Vft3h3oun+FyMvrWC9JORtTFraorM3yVFs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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