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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c50abc9b053448bb44429c4c606741d7d76ca0fc5f38d5ca8cd0446969170e65' 
  AND token = 'Up39aT+AtxrWMTl+v2SCAaUe5xsMlzvHxcGqlKSQVXc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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