SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b55dfa121ef3c067d8276384630de65ebe94863db4b2514fffc94e32e1210ba4' 
  AND token = 'u4aF3aTNBxIcnzS+arkheROYeYcuWZ54O1OhH/2hCds=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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