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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ebf55fdc14302ff42e2ccda479622744898158d774831ff0263539517a69a390' 
  AND token = '/6x4FMZi047VcLXM2b4A7CBtwJ9PHpiXcZELLolJ54s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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