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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56b5421d40878ee624ebd70abc483d656da01c9d9b00a71d19a278906a13e8ed' 
  AND token = 'K5KCobJXBAkM/Lz7TEdFlHxe+nYkyacQmkxGb+u0g6Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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