SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51e4cddde226d329485c360895279fb48f6bb6c5e1b699c60fe3b59a60d847bb' 
  AND token = 'uTztoLU7TxfuIop/eBWL2ThuG1zWjd4K08nwRwgn/ls=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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