SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81bd187516fffe2b09079919f8562003f02e2592ad54a8f5295dfe79826a4d81' 
  AND token = 'G21LE40KwF1V+MhBkCuQtqdLxr/yhYYwz999joLgWPU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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