SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a782af41e34e3be5230ee02c2b4746b298bc15a173299b0175af253b2f207473' 
  AND token = 'C9KjmUXfK892K5uecHpx6sEq3N2bLFvkyHuz3+y8q+s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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