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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9971371b525e4d992eeee1c9e96f493f58382284ce4efbc55a4d8bd3b330501c' 
  AND token = '7kQ9GjHeM7UaV5nZY/yeEgCG6AP0tT/GJlslOyB/VFo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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