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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e856c3ae863351c62f5df540c6282a03819c9657cf9eb1a730df55f0c98c6ade' 
  AND token = 'kB+e9fMDkuEZGMXCoPBUE2jje8y//g7W2fwSd3MYPq0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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