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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd3af5ad81b160a2d8425a7b74cdf43f1865da35f34f49556c4e54677d20d1f52' 
  AND token = 'sS6cIYJ8Zp2eeoQPh1wMO938YtyCW+JCPNQQa+ZOCBk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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