SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a536ee935af49edfe834fb39512b907e3b26fe1c92e94f7da23c462bd6f37a76' 
  AND token = 'h5gIrDN8lFEm/jiO5NGB7i2HxOVooiujTJW/bYuQqSk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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