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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c83e7870cb6b6a6b2fe09648a4ee1a2ea32f78c556fd0aa7c1d2f34f435e0f40' 
  AND token = '6RJSXeJb9cDNjU8zyVHZL2WCIZmWtTjUJ4ZnbXVYD0w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00008

JSON explain

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