SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0a0ae392b68af326eac71d93e246f65e17d59fd166dcbbd82d777189ca7683e6' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}