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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '729af0ef1bf0a0486e8f83ef348b6a3b495da4d2caf023d6b986054349c105f3' 
  AND token = 'U9rqdDqeupXCfJQpZbgr7kbtOdhMoxuB9YmULePFomQ=' 
  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"
    }
  }
}