SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5d1f7cf39414d118363e7255db8e9beb7cdae99f55995a5baa3e6a60681dfd7c' 
  AND token = '7iwjihk99jHr2rR2tpFgtdJmqLsFRBIR2Vmx+7MiTxM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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