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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b043ebbaab48d02b2e1eb45e8a58e12741b7a9b513c296052a01d9557bb58d7' 
  AND token = '71VKVBylA1714blZ0QWOk3oYFoKhkuBO8jiieklKKtE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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