SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bc143108872850032d458bf3b1b74be6be32578635d8daaa3e66a28a06b91237' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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