SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76a7d143fc5f29fd25e8f12739b85860a3a19e43fb00908f8bddb73113089836' 
  AND token = '3Kh54YDAiHrLm0O51HwgXT/hnUcXvoT7+BExqOmMkCg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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