SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c128462fb0626da976cdfee038b1d29769183332790d44840a33a528a179bd7' 
  AND token = 'lMmDElP5g+ugTtI3qVMRxnWn3S+uLcXW+5b2mdVuLqY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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