SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f340e1ba9e078628a0765745b12472ef311b41354caf5fd3508cedfc9da8120' 
  AND token = 'z2JqhbFtft1GvUYJim303QMSGUj2lldIzwllzEXZqOo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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