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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c61ec4b2d77dbbf807f33fced0a839b0ebefbb7aa0968d5a87cb3e2fc3f3bba4' 
  AND token = 'a/kFAvJs2fYp6QQR3MKsR5fTcU/GOYsiszXCpajrN9A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00056

JSON explain

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