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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ad9bc68021bd0a7eb408e1ac2da22ed2c584fd750750086bf78092b132cdae7d' 
  AND token = '5Qz1riLahAldkMzzFKDjS81NjEugCeDkoQCvauGM+xg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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