SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f2a81876b9a1ffa3139c10010108b6467b1e237027448c211a656c997eb09243' 
  AND token = 'p4gsvYTkZqWSCwov94CzBUpYzUEIds2+lfEdVqp0HAM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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