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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6946c9e0fda5e93ce67f736b4a955a46b6b14e797531e5b4cc36e69faae0b29' 
  AND token = 'jEzVBNW1KFTnAkHUJ+nQuV/I6DDZuiyGbzG0tOMSzSk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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