SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4c50a43f869f659958735df79b793ebd871702de78fbad3489f8333643fae1a2' 
  AND token = 'Jg+oq3mToP3uFUUfhHABIXMjobpNdtlRm5+JywuenXI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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