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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b12b341dcbf49194dfca1a995e3c5691fc76801968ca84a82d527cc25baf23b5' 
  AND token = 'MJwQlvxw/yg5vT7trwK0kC0j9NiuWkc0UOgt05vajsg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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