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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '836ef2e132fd9670cee1217f67e7d422bb12624d6622a7fd9cf784a0b76a45f3' 
  AND token = 'j1Fo2ztGdK7+vy1LgXoQTlEyYsiQsTTY0AwDPuJHf4E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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