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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '388f36b74a24f6fb1e9f794d81b59683ce689a2bb8941d9d38d4a917a29cb623' 
  AND token = '47q4ZL3i5fAmTg/oj4y7NT1jNNqnEVKrw2v5NjB957U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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