SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31db83da898624b1246b3434fb8f8fb4ec0bd627da5bc510aa456500e0391aee' 
  AND token = 'uXEVdv92eTzqbMejHvoOZHV6rU2cCdCdDWyXkjEyO20=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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