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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '620a5082536052cc8efeaf5fba76c5891c8afd2acbafe168c093b05733fbbf6f' 
  AND token = '7m2eIdb9FjFzjjqM+zkR3CKqFGL/8uO8sQ9Vcl/XgiQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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