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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8688fcf24e9bc7f061c71a6cda4c4a05ca45a2830d41f2ed2d9c48b12f42334' 
  AND token = 'CTh7ABvMWMxqRYv3NQHaVxJCSWNSwJ46X6yV75bBqgo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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