SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '77295049d2c6338f893a215b4e33df2411f2047c38bccb765a8e25a922a8762d' 
  AND token = '4eRlVnYAFKo1N8YPJtzbRb4wa3xn9TQBE5wELlPoFmY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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