SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6ea3e7498352e8e8d0ffa99156fa547e6f46efd2d63f9e3878a5790b1e3a2ab' 
  AND token = 'uPN+VBvuPROhJGSk0EgKjssiI/Ea8W0vxsYXHVtEMJ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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