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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b8cbf264e2fa3f87bd1f2cb58f079047a5262d3f6356af34b52f8498b5dfa6b' 
  AND token = '7TKBmAxj7LZupZZLKyNIevzkSWRDJmcKi6Z6NOaAB1E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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