SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a6c6f200ed1b0a00d02be4063f9d51c754e7453fb4ffc60087ca384a85db274' 
  AND token = '+SZUC8ANsjGb6VRAInKaOKsxSm9ImxU3B+z2HmJOhLM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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