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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e51292bd90b6bc76a019d207b8601fdb4b41c0a58f9e5c0d4d1a35ba3e2a6652' 
  AND token = 'D+PyNNtKjDkVqxCINVrdSoHWrUgVuYhy1QmCdx0lFqg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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