SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3273a51affefc5fc12b76719d2766cfb2f90f4fd14ca6d2561195fabf43e95a7' 
  AND token = 'lWVLe9ZcmI+Mhros6CAOZPzvTNQFbuR1U2cMYYuy4w0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}