SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a9dc79b7218c6ff926bec11a7063d56a5592c943d6787caacd2368f3f94f450' 
  AND token = 'U/rCvzRwvBqIwGrCW92BQdNK1Rri67ZUUCQDxFlze88=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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