SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6cd21fbc4e6c8edbb3731245f6d814c4f936860ebd56fc47a325b5e9f778af7' 
  AND token = 'nzmV+5aISB3+FX+W+lt2chYGZBIL9at/MFWsltCDpVw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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