SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '49e708e5be8d3de9606a0f36f22cb16bf1c9f8a1c1f56d7ecde95b50f5e58edb' 
  AND token = 'Iw+Dn0zt5hG2EV8GmhovXBRPFPKNhpUHY/K/MUY0Nn0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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