SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57b64332411ee6bffb07720d64ceaa0cc468d71dd90b9a953f431e5c20b9c50a' 
  AND token = 'nV2yq5fta+CjTYTYsxEd8Nvo3Xep6MLOT23GGKyFvZM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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