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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '38dca3e97719d7154b7b8fed40896942faa1421c63bb2c31b2d3f42047af3aa9' 
  AND token = 'QK0RQ3W7+7mTwSscrSeUKIYPBjVHr4YU3EiN7Ft1DMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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