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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55b0b386f106775aa62d48c006ebf39c24d407c2c7679478eb04a429678a984d' 
  AND token = '8XQ/eJxMqMNd6+ormMDZlkcqqN7N4sL9kx/WAwvvDys=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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