SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'de6c82eba54f28f3c21958e677a596e930a8657e0081631d709c966993404a4e' 
  AND token = 'Sd2xck2xrB+q41euO/6uSLwb/Q0Zokc7G8d3gbnsukQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00010

JSON explain

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