SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c374d6f5e0cfaf5688c532786fc0589cd926839e9306f4bf93ad03244263fba2' 
  AND token = 'xtYFVZYrTKYJQsNnga104dm92zwGbnfeLvTGstjiueI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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