SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b718003632e3f3b1f5dc6e57fcfdcfa8dd6eb9640cd8d49785a6b51fa06d2b56' 
  AND token = 'DAvQkeiCYMrCKTrMLFvpz3JbWcwVSl1jomgOGZByMu0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00059

JSON explain

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