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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'db50ce386b08fdc4f1ad1fcb148d0e40041f3a442f1d09978b5a43558b84fdea' 
  AND token = '2pUr+ZqbxgO+F7HuaXfY5PnxDW6SBXdbm0dmRcyKu0k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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